What CECO PDF does, and what it refuses
CECO PDF fixes the wrong word in a PDF or a scan, in the document's own font, and checks that nothing else on the page changed. It also edits, redacts, merges, splits, compresses, converts and signs PDFs. It refuses identity documents and a match it is not sure of, offers no replace-all, and never covers words with a white box.
Every figure below is read from the code that enforces it, when this page is served. One correction, start to finish, is on How it works. How corrections stand up to forensic detectors is on Measured results. What each plan costs is on the pricing page, and the API is in the API documentation.
What can CECO PDF do?
It has 19 tools, each with a page of its own, and Fill & sign in the document workspace where you correct. The tools page groups them as the home page does.
| Tool | What it is for | What it makes |
|---|---|---|
| Correct text | Change a wrong word, date or number | The same PDF with the words corrected, checked, and a record of each correction inside it |
| Fill PDF | Fill in a form’s fields and blanks, in Fill & sign | A finished copy with the answers set on the page, or a copy with form fields to fill in later |
| Sign PDF | Place your own signature or initials, in Fill & sign | A copy with your own drawn, typed or uploaded mark where you placed it |
| Edit PDF | Add text, images, shapes, highlights and notes | The same PDF with text boxes, images, shapes, highlights or notes laid over its pages, each removable, and a record of each; a word changed on the page is a correction |
| Merge PDF | Join several PDFs into one | One PDF, with every page of each file in the order you set |
| Split PDF | Cut one PDF into several | Several PDFs: every so many pages, by ranges you write, or by size |
| Extract pages | Make a new PDF from chosen pages | A new PDF of the pages you name, in the order you name them |
| Remove pages | Take pages out of a PDF | A copy without the pages you name |
| Reorder pages | Put pages in a new order | A copy with every page in its new place |
| Rotate pages | Turn pages the right way up | A copy with the pages turned a quarter, a half or three quarters |
| Watermark | Stamp text across every page | A copy with words or an image drawn over its pages |
| Page numbers | Number every page | A copy with page numbers, a header or a footer |
| Bates numbers | A running number on every page of a legal set | Each document as its own file, its pages numbered in one run |
| Compress PDF | Make the file smaller to send | Smaller copies to choose from, each with its exact size, or the best-looking one under a size you set |
| Protect PDF | Add a password | A copy that needs a password to open, or limits what it may be used for |
| Unlock PDF | Remove a password you know | A copy without its password, once you give the password |
| Redact PDF | Remove words, areas and images for good | A copy with the words, areas and images you chose removed from the file, a mark drawn where they were, and a record that never quotes them |
| Compare PDFs | See what changed between two versions | Every change between two versions, numbered, with the words that changed |
| OCR PDF | Make a scan searchable and copy its text | From a scan: a searchable PDF, plain text, text laid out as the page has it and a CSV of each page that is clearly a table |
| Convert to PDF | Turn photos, documents or web pages into a PDF | One PDF from your photos, documents, text files or saved web pages |
| Convert from PDF | Export images, text, Word or Excel with a fidelity record | From a PDF: PNG, JPEG, plain text, text laid out as the page has it, Word, Excel or PDF/A, with a record of what the format kept and lost |
Which files can it take, and which can it make?
Every tool takes PDFs but the converter, which makes PDFs from other files. A file is judged by what is in it, never by its name.
| Tool | Takes | Makes |
|---|---|---|
| Edit PDF | A PDF; for an image laid over it, a PNG or JPEG of up to 2 MB | The same PDF, with annotations over its pages |
| Convert to PDF | Pictures: JPG, PNG, TIFF, HEIC, WebP and AVIF. Text: plain text, Markdown and HTML. Office files: .docx, .xlsx, .pptx, .doc, .xls, .ppt, .odt, .ods and .odp. | One PDF, each file starting on a page of its own |
| Convert from PDF | A PDF | PNG, JPEG, plain text, text laid out as the page has it, Word, Excel or PDF/A, and a record of each export |
| OCR PDF | A PDF that is a scan or a photograph | a searchable PDF, plain text, text laid out as the page has it and a CSV of each page that is clearly a table |
| Compare PDFs | Two PDFs: an earlier version and a later one | The changes on screen; a PDF report and a CSV of the words that changed |
| Fill PDF and Sign PDF | A PDF; for your mark, a PNG or JPEG of up to 2 MB and 4 million pixels | A PDF: a finished copy, or a copy with form fields |
| Correct text, Merge PDF, Split PDF, Extract pages, Remove pages, Reorder pages, Rotate pages, Watermark, Page numbers, Bates numbers, Compress PDF, Protect PDF, Unlock PDF and Redact PDF | PDF: one file, or one for each part or document |
What are the limits on each plan?
A file over its plan's limit is refused when it is uploaded, and the message names the limit. These are the numbers the service enforces:
| Plan | Largest file | Corrections | Files kept |
|---|---|---|---|
| Free | 15 MB and 50 pages | 10 corrections a day. | 90 days |
| 1 document | 50 MB and 50 pages | Unlimited corrections while a credit is unspent, for up to 30 days after buying, then 10 a day. | 90 days |
| 10 documents | 50 MB and 50 pages | Unlimited corrections while a credit is unspent, for up to 30 days after buying, then 10 a day. | 90 days |
| Personal | 100 MB and 100 pages | No daily limit on corrections. | 90 days |
| Business | 100 MB and 300 pages | No daily limit on corrections. | 90 days, or a period you choose |
Some things come only with some plans:
| What | Plans |
|---|---|
| Verification certificates, which anybody can check at a public page | Business |
| Priority processing, on a share of the engine kept for Business | Business |
| API keys, to use CECO from your own software | Business |
| The record of every change, as a file you can hand over | Business |
| Your choice of how long documents are kept | Business |
A few tools have limits of their own:
| Tool | Limit |
|---|---|
| Compress PDF | Files up to 100 MB, on every plan |
| Convert to PDF | Up to 50 files at once, 32 MB of them in all on every plan, and no file over the size your plan uploads. A picture of more than 100 million pixels is refused, and the line is lower for one that has to be decoded first. |
| Edit PDF | Up to 50 items in one step; an image up to 2 MB |
| Redact PDF | Up to 200 regions in one request; a label of up to 40 characters; a word to find of at least 3 characters |
| Unlock PDF | 10 tries in 10 minutes from one address |
| Protect PDF | A password of up to 40 characters |
| Sign PDF | A mark uploaded as a picture, up to 2 MB and 4 million pixels |
Which downloads cost nothing?
Correcting is free to try, with a watermark on the corrected pages until the document is paid for, unless you are signed in and have not yet taken your first corrected download of the day. Signed in, your first corrected download each day costs nothing; after it, downloading a corrected document takes a credit or a plan. Several tools download at no cost when nothing in the file was corrected here: text boxes, images, shapes, highlights and notes laid over a page among them, while a redaction is priced as a correction.
| Plan | Price | Corrected documents it downloads |
|---|---|---|
| Free | €0 | Signed in, your first corrected download each day; after it, none until the document is paid for |
| 1 document | €0.99, once | 1 document, which downloads again at no cost |
| 10 documents | €4.99, once | 10 documents, each of which downloads again at no cost |
| Personal | €9.99 a month, or €89.99 a year | Every document, as often as you like, while the plan runs |
| Business | €24.99 a month, or €224.99 a year | Every document, as often as you like, while the plan runs |
Each tool says its rule beside its download button, in these words:
| Tools | Their download |
|---|---|
| Correct text | Signed in, your first corrected download each day costs nothing; after it, one takes a credit or a plan. |
| Edit PDF | Downloading costs nothing when all you did was add text boxes, images, shapes, highlights or notes, or crop, flatten or repair the file. Changing a word on the page is a correction, and downloads as a corrected document does. |
| Merge PDF, Split PDF, Extract pages, Remove pages, Reorder pages, Rotate pages, Watermark, Page numbers, Bates numbers, Compress PDF and Convert to PDF | Downloading costs nothing when the files you started from have no corrections made here. A file made from a corrected document is priced as one. |
| Protect PDF and Unlock PDF | Your file is sent once and handed straight back. Nothing is kept here. |
| Redact PDF | Downloading the redacted document is priced as a corrected document is. |
| Compare PDFs | The changes are shown here. The report and the list of changes to download come with a plan, or a pack bought in the last thirty days. |
| OCR PDF and Convert from PDF | Downloading costs nothing when nothing in the file you read was corrected here, even if it was merged, split or turned here first. A file made from a corrected document is priced as one, and so is one we can no longer trace back to the files it was made from. |
| Fill PDF and Sign PDF | Saving a filled or signed copy counts as one correction. Downloading the result is priced as a corrected document is. An empty fillable copy counts as none, and downloads at no cost when nothing in the file was corrected here. |
How is each correction checked?
Every correction is checked before it can be downloaded, and the check is a statement about the picture of the page, made by the service about its own output.
| Part | What it is |
|---|---|
| Resolution | Each page is rendered before and after, a scan at 300 dots per inch and a page of real text at 150, and the two pictures are compared pixel by pixel. |
| What passes | Every changed pixel lies inside the region the correction declared, so the count of changed pixels outside it is 0 on every page. The result shows it as outside 0 px. |
| What counts as a change | Any difference at all: the tolerance is 0. |
| The guards | The text is where it was measured to be, the edit kept to its own line, and the letters came through whole. |
| The download | Closed until the check passes. A document changed after it was verified is verified again before it can be downloaded. A failed result offers to undo the correction. |
| What it does not say | That the corrected words are true, or that the document is accurate, lawful or acceptable to whoever receives it, or that anybody was entitled to make the change. |
The fields the API returns for each check are in The verification model.
What does it refuse?
A correction that cannot be made well is refused rather than made badly. The refusal says what happened and why, and your document stays as it was.
| Refused | What happens, and why |
|---|---|
| Identity documents | Refused when they are uploaded, and deleted with everything made from them. The terms name the kinds. |
| A document already issued | Fill & sign refuses a page that reads as an issued document, whole. When a page you correct carries marks of having been issued, the app says so: for a document already issued or served, the clean route is a corrected re-issue rather than a retouch. |
| A match it is not sure of | When a word appears more than once and the reading is not certain which one you mean, the correction is refused. Correcting the wrong one would pass the check and still say the wrong thing. |
| Replace-all | Not offered. Each place a word appears is its own correction, made and checked on its own. |
| A white box over words | Never used. On a page of real text, the new words are typed into its text, and no picture of words is painted over it. On a scan, the space the old words leave is filled to match the paper around them; when that paper cannot be reproduced, the correction is refused. |
| A stamp, a rule or a fold across the words | Refused: moving the ink would cut through the mark. |
| Drawn letters that would not match | Refused when they would come out sharper than the scan around them, or when the typeface cannot be identified with confidence. |
| A word read without confidence | Left out of a reading rather than guessed, and counted. A page that cannot be read with confidence is named as unreadable. |
| A password you do not have | Unlock opens a file only with the password you give. It is not a password cracker: 10 tries in 10 minutes from one address is all anybody gets. |
| Taking off a watermark or a Bates number | Refused. A correction that would take away any part of one is not made. |
| Covering words with a box | Refused by Edit PDF: a box or a text box that would hide what is already on the page is not an edit, as the words would stay in the file. Words are changed by a correction, in place, and taken out for good by a redaction. |
| Redacting a watermark, a signature, a seal or a security feature | Refused by Redact PDF, whoever asks: a region that holds a watermark, a Bates number, a signature or initials, a seal or stamp, microprint and a guilloche pattern (fine security line art) is left as it was, and named. Removing those is how a document is disguised or falsified. |
| Changing a digitally signed PDF with the editor or redaction | Refused whole: any change would break the signature. Work on a copy that has not been signed, then sign it again. |
| Redacting everything that matches | Not offered. Each region is drawn, or each match ticked, before anything is removed. |
| Signing for somebody else | Refused. Fill & sign places only a mark you confirm as yours, never over ink or another signature, and never on a PDF already signed digitally. |
Whose documents is it for?
Your own, or ones you are entitled to alter. It is made to fix a date you typed wrong in your own document, to correct a figure in a document you wrote, before you send it, and to fix a misspelt name in your own letter or form. Editing a signed PDF breaks the signature; correct it, then sign it again. Open your own protected file with its password.
CECO PDF does not try to judge who is entitled, because no automated check can; it records instead. Using it to forge, falsify or misrepresent a document is a misuse of the service and, in most places, a criminal offence, and accounts doing so are closed, as the terms say.
What does it record?
Every change is recorded, inside the file and on the service, so anyone can see what was done.
| What | What it holds |
|---|---|
| The record inside the file | Every correction, where on the page it was made and how, in an attachment named provenance.json that names the file as a corrected copy. It is a claim, not proof: anyone holding the file can strip it. |
| The service's own record | Every upload, correction, undo, export and download, append-only. Each entry carries the hash of the one before, so a break in the chain shows. |
| Your statement | Every correction carries it, in these words: “I confirm I am authorised to alter this document. I understand that if it has already been issued or served, the appropriate route is a formal correction or a corrected re-issue, not a retouch. I accept responsibility for this change.” |
| The engine's version | Every correction's record names the version that made it. |
| Forms and marks | Where each answer and each mark went, and a fingerprint of the mark, never the answers or the mark itself. |
| Editing steps | What was laid over which page, each annotation by its name, a crop's boxes before and after, and what a flatten baked in; a text box's words only as a fingerprint. |
| Redactions | Which regions of which pages, how many runs of text, images and drawings went, and the mark drawn, never what was removed. |
| Handing the record over | With a Business plan, the whole record exports as a file. |
| A verification certificate | With a Business plan: the document's SHA-256 hash as uploaded and as corrected, every correction with its measurement, and the head of the record when it was issued, signed with Ed25519. |
| Checking a certificate | Anyone can, without an account, at the certificate check: by its id, or by uploading it. The public key is at /.well-known/ceco-certificate-key. |
Which languages can it read on a scan?
Choose the language in the OCR tool, or let it find the language. Then it works out the writing system first, and tries these:
| Writing system | Languages tried |
|---|---|
| Latin letters | English, Albanian, German, French, Italian, Spanish, Portuguese, Dutch, Croatian, Serbian (Latin), Turkish, Polish, Czech, Romanian and Hungarian |
| Cyrillic | Russian, Serbian (Cyrillic), Ukrainian, Bulgarian and Macedonian |
| Greek | Greek |
| Fraktur (blackletter) | German (Fraktur) |
English and Albanian are tried on every page, whatever its writing system. A page in another writing system is tried in the languages the server has for it. Any language the server has can also be chosen by name: the OCR tool lists them.
How well it reads was measured on invented pages in English, Albanian, German, Croatian, Serbian (Cyrillic), Russian and Greek. Every other language is read, not measured.
How this is known: the lists above are the reader's own, read from its code when this page is served. Which languages are installed is a fact of the server, so the tool lists them rather than this page.
Which version is running?
The version below is the one serving this page.
| Part | What runs |
|---|---|
| The engine that makes and checks corrections | Version 0.1.1 |
| Word, Excel and PowerPoint files | Laid out by LibreOffice, apart from the rest of the service, with no connection to the internet. Each conversion's record names the version. |
| Archival PDF/A copies | Handed over only once the veraPDF validator has passed them. |
Where are my files kept, and for how long?
Documents are stored under the account that uploaded them, and no part of the service shows their contents to anyone else. They are not used to train anything.
| What | How long |
|---|---|
| Documents you upload, and what the tools make from them | 90 days, or until you delete them. With a Business plan, you can choose the period. |
| A document as it was before an editing step or a redaction | Kept with the document, so that undo can bring it back, until the document is deleted. Delete it once you have a redacted copy, if the original should not stay. |
| Files you convert into a PDF | Only until the conversion has answered. The PDF is kept like any other document. |
| The sizes compress makes | Deleted an hour after they are made, or as soon as you choose one. |
| A file you protect or unlock from your computer | Not kept at all: it is sent once and handed straight back. |
| A part of a page you choose to report | 365 days, and only if you press the button that sends it. No box starts ticked. |
| Your file's name | It stays in your browser. Only its length and its extension reach the service, unless you print a name on a certificate. |
| Everything | You can erase it yourself, at any time, without asking anyone. |
The privacy notice says what is kept, why and for how long.
Where is each part explained?
- How it works: one correction, start to finish, and the check.
- Measured results: how corrections stand up to forensic detectors, measured on invented scans.
- Pricing: what each plan costs and allows.
- API docs: the same service from your own software.
- All tools: every tool, grouped.
- Terms: who may alter a document, and what a verified correction means.
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