Google Drive annotates PDFs on Android: pen, highlighter, eraser, undo, and a choice of saving over the file or keeping a copy. That is annotation, and for most of what people want it is enough.
Rearranging pages and changing the words are different jobs. Neither is built into Android, and the second one is hard everywhere.
Searching for a PDF editor on Android turns up a hundred apps with the same screenshots and an unusual density of subscriptions. Working out which job you have first saves most of that.
Three jobs, one word
What Drive already does
Open a PDF in the Google Drive app and there is an annotate button in the bottom right. Google's page for it lists what the toolbar holds: marker, highlighter, eraser, undo and redo, and a switch to show or hide the annotations.
The detail worth knowing is the save. It will either write over the original or keep a new copy under a different name, and it asks. Choose the copy unless you are certain, because an annotation saved over a form somebody has to fill in later is a nuisance to undo.
One thing it is not is a redaction tool. A black stroke drawn over a name is a black stroke on top of a name, and the name is still in the file for anybody who selects the area and copies it. If something has to be genuinely gone, the text has to come out of the document rather than be covered, which the redaction tool here does and then verifies by reopening the finished file.
Rearranging, which is the common one
Merging two documents, pulling out three pages, rotating a sideways scan, getting a file under an upload limit. None of these change a word of the document and none of them are built into Android.
Nothing to install and nothing to subscribe to.
The same tool as on a laptop, at the same address.
A tool that works in the page does not upload the file.
Chrome on Android handles the file picker and the download.
Works with no connection at all.
Integrates with the share sheet, which is genuinely convenient.
Storage, updates, and usually a subscription.
Worth checking what it uploads before you give it a document.
The tools here are the first column: merge, split, rotate, compress, reorder pages. They run in Chrome on the phone and the file stays on it.
Judging an app from the store
If an app is the right answer, the listings are hard to tell apart on purpose. Four things separate them, and none of them are in the screenshots.
Where the work happens
An app that needs a connection to rotate a page is doing it on somebody's server, which means your document goes there. The description rarely says; the permissions and the behaviour in aeroplane mode both do.
What it does with the free tier
A watermark on the output, a page limit, or a trial that bills. Worth finding out before the document, not after.
What it asks for
A PDF tool does not need contacts, location or the microphone. Storage and nothing else is the shape to expect.
Whether it keeps a copy
Cloud sync is a feature and it is also a copy of your document on a server. Fine for a leaflet, worth thinking about for a payslip.
None of that is an argument against apps. It is an argument for knowing which one you are installing, particularly for the jobs that only take a few seconds, where the trade of a subscription and a copy of the file against a browser tab is a poor one.
Changing the words, which is the hard one
This is the job people assume is easiest and it is by far the hardest, on every device. A PDF does not store paragraphs. It stores instructions for drawing glyphs at coordinates, so changing a word means re-laying out the line, and possibly the page.
Uploading to Google Docs will convert a PDF into an editable document, and it will lose the layout doing it: Docs re-flows the text into its own formatting. That is fine for getting the words out and poor for keeping the document looking like itself.
The honest route is to convert deliberately, edit in something that edits, and go back. PDF to Word or PDF to Markdown for the text, then edit, then back to PDF. Every step of that runs in the browser.
Expect the layout to move. A converter rebuilds paragraphs, headings and tables from where the glyphs sit, and it gets most of them right and some of them wrong. For a letter or a report that is a few minutes of tidying. For a form, a brochure or anything laid out in columns it is not worth attempting on a phone, and honestly not worth attempting at all: ask whoever sent it for the original.
Do the rearranging in Chrome
Merge, split, rotate and compress on the phone, with nothing installed and nothing uploaded.
Common questions
What Drive does, what it does not, and which job you actually have.
01Is there a PDF editor built into Android?
Google Drive annotates PDFs with a pen, a highlighter and an eraser, and lets you save over the file or keep a copy. There is no built-in way to merge, split or compress, and nothing on any platform edits the existing text directly.
02How do I annotate a PDF on Android?
Open it in the Google Drive app and tap the annotate button in the bottom right. A toolbar appears with the pen, highlighter and eraser. Google's documentation notes it needs Android 6 or later and works with a finger or a stylus.
03Can I merge two PDFs on my phone?
Not in Drive. A browser tool will do it in Chrome, and the ones that work in the page do not upload the files. An app will do it too, at the cost of storage and usually a subscription.
04Why can I not just edit the text?
Because a PDF stores glyphs at coordinates rather than sentences, so changing a word means re-laying out everything around it. The way round it is converting to a format that does store sentences, editing there, and converting back.
05Does uploading to Google Docs work?
For getting the words out, yes. Docs converts the PDF into an editable document and reflows the text into its own formatting, so the layout does not survive. Useful for the content, poor for keeping the document looking like itself.
06Are browser tools safe for private documents?
It depends entirely on whether the tool does the work on your device or on a server. Ones that run in the page never send the file. Check before you hand over anything with a name and an address on it.