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What is Signature PDF?
Signature PDF is a free, open-source web tool for signing and manipulating PDF files. It runs in the browser and requires JavaScript to function. According to the page, it is licensed under AGPL-3.0 and its source code is available.
What you can do with it
- Sign: add a signature, initials, a stamp, typed text, strikethrough text, a watermark, or sign with the server certificate. Multiple people can sign through a shared link.
- Organize: combine PDFs, reorder, extract, rotate or delete pages, change or standardize paper size, generate a booklet, and convert images to PDF.
- Metadata: add, edit or remove PDF metadata, plus OCR to detect text in images inside a PDF.
- Compress: reduce PDF file size.
Who it suits
It fits people who need quick PDF edits without installing desktop software, and those who prefer an open-source tool they can inspect or self-host. The shared-link signing is useful for small teams collecting signatures from several people. The interface is available in many languages, including English, French, Spanish, German, Arabic, Tamil and Turkish.
Trade-offs
Browser-based tools depend on JavaScript and an internet connection, so they are less convenient for offline or highly sensitive documents than local software. Server-certificate signing means the signing process involves the service's server, which may matter for confidential files. Open source and AGPL-3.0 licensing give transparency and the option to run your own copy, but self-hosting requires technical effort.
As a next step, open the site and test one task on a non-sensitive PDF first, such as compressing a large file or adding a watermark, to see whether the workflow and output quality match your needs.
How do I sign a PDF with multiple people using a shared link?
Use Signature PDF's shared-link flow: you upload the PDF, add the signature fields, and let each participant sign through a link rather than passing the file back and forth. On Signature PDF, this appears as part of the signing toolset, alongside adding signatures, initials, stamps, typed text, strikethroughs, a watermark, and signing with a server certificate.
How the shared-link workflow typically goes
- Open the PDF in the signing tool and place a signature field where each person needs to sign.
- Add initials, a date, or typed text fields if the document requires them.
- Generate the shared link and send it to the participants.
- Each person opens the link, signs in their assigned area, and submits.
- Download the completed PDF once all signatures are in.
The main advantage is coordination: you keep one master file and one link, so you always know which signatures are still missing. The trade-off is that the document lives on a server while the signing is in progress, and participants need a browser and a working connection. For a one-off signature from a colleague in the same office, a simple downloaded-and-returned PDF may be faster; for a contract with three or four signers in different places, the shared link saves real time.
Practical checks before you send the link
- Confirm every signer has a clearly labelled field, so nobody signs in the wrong place.
- Decide whether you need initials, dates, or a stamp in addition to the signature.
- If the document contains sensitive data, check your organisation's rules on uploading it to an online tool.
- After signing, verify the final file and store the completed version yourself rather than relying only on the link.
If the PDF is also large or has odd page sizes, Signature PDF's other tools for organizing, rotating, resizing, combining, and compressing pages can be used in the same session before you send it out.
How can I combine, reorder, or extract pages from PDF files?
For combining, reordering, and extracting pages, use a browser-based PDF editor that exposes those operations directly in its toolbar. Signature PDF lists all three under its Organize section: Combine multiple PDF files, Reorder pages, and Extract pages, alongside Rotate pages, Change or standardize the paper size, Delete pages, and Generate a booklet. Because it is free open-source software (AGPL-3.0) that runs in the browser, you avoid installing a desktop suite for what is often a one-off task.
Which operation fits your situation
| Goal | Operation | Typical use |
|---|---|---|
| Merge a signed contract, an annex, and an ID scan into one file | Combine | Assembling a submission packet |
| Put a cover page first or move an appendix to the end | Reorder | Fixing scan order |
| Pull out only pages 4–7 to send to a colleague | Extract | Sharing a single chapter or invoice |
| Remove a blank or duplicate page | Delete | Tidying a scanned document |
| Make all pages A4 before printing | Change or standardize paper size | Print consistency |
A practical workflow
A concrete scenario: you have three separate scans of a ten-page report and need one correctly ordered file. Combine the three PDFs first, reorder the pages into the right sequence, delete any blank backs, then extract nothing at this stage — extraction is best done last, only when you actually need to hand a subset to someone else. Extracting before merging means you lose the surrounding context and may have to merge again.
Two trade-offs worth knowing. Browser tools depend on JavaScript, and this site states plainly that it is not functional without it, so enable JavaScript or the interface will not load. Also, upload-based online tools mean your file leaves your machine; for contracts, medical records, or anything confidential, check whether the tool processes files locally in the browser or on a server, and prefer a local process or a desktop alternative when the document is sensitive.
As a next step, open the Organize section, combine your files, then use the page thumbnails to drag pages into order before exporting. If you only need to sign rather than restructure, the same site handles signatures, initials, stamps, and multi-person signing via a shared link, so you can finish the whole job without switching tools.
How do I compress a PDF to reduce its file size?
Use Signature PDF when you want a browser-based, open-source tool for the job: its Compress section is built to "compress and reduce the size of a PDF." The workflow is deliberately plain — open the site, pick Compress, upload your file, and download the smaller result. Because the tool runs in the browser, nothing needs installing, but JavaScript must be enabled or the page won't work at all.
What actually shrinks a PDF
Most size reduction comes from one of these, and knowing which applies to your file tells you what to expect:
- Downsampling images. Scanned pages and photo-heavy documents are usually the biggest offenders. Lowering image resolution or re-encoding images as JPEG cuts the most bytes, at some cost to sharpness.
- Removing redundant objects. Editing and merging often leave orphaned fonts, duplicate resources or unused metadata behind. Cleaning these up is nearly lossless.
- Dropping embedded fonts. Subset or remove fonts you no longer need — risky if the text must stay visually identical.
- Flattening or simplifying structure. Helpful for forms and annotations, but it can make the file harder to edit later.
A practical scenario
Say you have a 40-page scanned contract at 25 MB and a portal that rejects anything over 10 MB. Compressing is the right first move; if the scan is the problem, expect the text to look slightly softer after compression. If the compressed file still fails, split it — Signature PDF's Organize tools let you extract pages, so you can send two smaller parts instead of one oversized file. If the document is mostly typed text with few images, compression gains will be modest, and re-exporting from the original source is often better.
Choosing between options
| Situation | Sensible approach |
|---|---|
| Scanned or image-heavy PDF | Compress; accept mild quality loss |
| Typed text, few images | Try compression, but expect small gains; re-export from source if possible |
| File must stay editable | Prefer lossless cleanup over aggressive image downsampling |
| Still too large after compressing | Split into parts or reduce page count |
For a second opinion or a different compression engine, Smallpdf and iLovePDF are well-known alternatives, though both are commercial services rather than open source.
As a next step, compress a copy rather than your only version, then open the result and check the smallest text and any signature or stamp before sending it on.
How do I add, edit, or remove metadata from a PDF?
Use the Metadata tool on Signature PDF to add, edit, or remove a PDF's document properties — the fields such as Title, Author, Subject and Keywords that travel inside the file itself. Open the site, choose Metadata, load your PDF, change the fields you need, then download the result.
What the workflow looks like
- Open the Metadata tool and select your PDF.
- The existing metadata fields are read from the file so you can see what is already there.
- Edit a field to change it, or clear it to remove that value.
- Export and download the updated PDF, then reopen it to confirm the properties panel shows what you expect.
When this matters
- Publishing or archiving: set a clear Title and Author so the document is identifiable outside its filename.
- Privacy cleanup: strip Author, company or software strings before sending a file to a client, journalist or public portal.
- Batch consistency: standardise Subject and Keywords across a set of reports so they sort and search predictably.
Practical cautions
Metadata edits change only the document properties, not the visible page content — a name typed into the body of the PDF stays there. Some viewers also cache properties, so re-download rather than relying on a preview tab. If your PDF is a scan, the text layer is a separate problem from metadata; that is what the site's OCR option addresses.
If you need a desktop alternative for offline or bulk work, ExifTool is the standard command-line tool for reading and writing PDF metadata, and QPDF handles structural rewrites; both suit scripted workflows better than a browser page.
What does the OCR feature do for text detection in PDF images?
The OCR feature detects text contained in images inside a PDF, turning those pictures of words into content you can search, select and copy. On Signature PDF it sits alongside the signing, organizing, metadata and compression tools, so it is best understood as a way to rescue text that would otherwise be locked inside a scan or screenshot.
What that changes in practice
- A scanned contract or photographed page becomes searchable, so you can find a name or clause with Ctrl+F instead of reading every page.
- You can copy a paragraph, an invoice number or a reference code and paste it into another document.
- The text layer can support later editing, indexing or accessibility workflows, depending on how you use the result.
Where it fits and where it does not
| Situation | OCR helps | OCR does not help |
|---|---|---|
| Scanned pages, photos of documents, image-only PDFs | Yes — this is the core case | — |
| PDFs that already contain real text | No need; text is already selectable | Running OCR adds no benefit |
| Handwriting, unusual fonts, low-resolution scans | Sometimes, with errors | Accuracy can drop sharply |
| Complex layouts, tables, multi-column pages | Partially | Reading order and columns may come out jumbled |
A useful next step
If you have a scanned PDF, run OCR first and then check a few random pages: select a sentence and paste it into a plain text editor. If the words come through cleanly, the recognition worked; if you see garbled characters, the scan quality or layout is the limiting factor, and a higher-resolution scan is the practical fix. For documents you also need to sign or reorganize, doing OCR before those steps keeps the text layer intact. Adobe Acrobat Adobe Acrobat offers comparable OCR in a commercial suite, while PDF24 Tools provides free browser-based PDF utilities if you want a second option for a quick job.
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