PDF apps for reading, marking up and signing on a phone
PDF is four different jobs wearing one file extension. Reading a book-length document, marking up a contract, filling in a form someone emailed you, and signing something before a deadline all need different things from an app. Pick by the job rather than by the star rating.
Match the app to the job
| What you need to do | What matters | Pick |
|---|---|---|
| Read a long document | Reflow, night mode, position memory | A reader built for books |
| Mark up a draft | Highlight, comment, export with annotations intact | A full annotation app |
| Fill in a form | Form field support, not just drawing on top | An app with real form handling |
| Sign and send back | Signature placement and flattening | An annotation app with signing |
| Open a 200 MB technical manual | Rendering speed and memory handling | A lightweight native renderer |
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Reading and marking up
The most complete free annotation set on Android: highlights, comments, shapes, signatures and form filling, with annotations that survive being opened elsewhere.
Built for large documents. Fast rendering, reflow for text-heavy files, and a genuinely good night mode with adjustable contrast.
Tiny, no account, no cloud. If all you want is a renderer that opens the file instantly and does nothing else, this is it.
A reader that handles PDF alongside EPUB and DjVu, with per-document settings and a library view that makes sense for a large collection.
When the PDF is really a document
Sometimes what you need is not annotation but conversion, because someone sent a PDF of something that should have been editable.
Converts PDF to editable text and back, and handles Word and Excel files in the same app. The most capable office suite on Android by a wide margin.
If the document must come back looking exactly right on a colleague's PC, the first-party app removes a category of formatting arguments.
A lighter office suite that opens PDFs and Office formats without the account requirement.
Making a PDF from paper
The opposite direction is just as common: someone needs a signed page back as a PDF, and photographing it produces a grey lopsided image nobody wants.
Edge detection and perspective correction that genuinely work, plus multi-page documents. The free tier watermarks, which is worth knowing before a deadline.
Cleaner free tier than most, good batch scanning, and export straight to PDF without an account.
- Scan with a document app, not the camera
- Flatten annotations before sending
- Check the file opens on a computer before you send it
- Keep the original if you signed a copy
- Photographing a page in the gallery app
- Renaming an image to .pdf
- Sending a 40 MB scan when 2 MB would do
- Signing on top of a form with real fields
Decide whether you are reading, marking up, filling in or signing. Each needs a different app, and using the wrong one is why PDFs on a phone feel harder than they should.
Frequently asked questions
Which app can fill in a real PDF form?
Xodo handles interactive form fields properly, as do the paid tiers of most office suites. Simple readers cannot.
Are my annotations visible to other people?
Standard PDF annotations are, if the app wrote them as annotations rather than as a private layer. Flattening removes any doubt.
Why is my scanned PDF so large?
It is storing full-resolution photographs. Scanner apps have a quality setting, and black-and-white document mode cuts the size dramatically.
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