How to Edit a PDF Online: Rotate, Watermark, Add Page Numbers
Most of the time when someone says they need to "edit a PDF," they don't actually mean rewriting the text — they mean something much smaller: a page scanned in sideways, a report that needs "DRAFT" stamped across it before it goes out, page numbers missing from a document that's about to be printed and bound. None of that needs a full PDF editor license, just the right small tool for the specific fix.
Rotating pages that scanned in sideways
This happens constantly with scanned documents — a page fed into a scanner the wrong way ends up sideways or upside down in the resulting PDF, and it's not always obvious until you actually open the file and start scrolling. Rotate PDF fixes this page by page or across the whole document, and it's usually the very first thing worth checking on any scanned PDF before you do anything else with it — reading a sideways page is annoying enough that it's worth fixing immediately rather than working around it.
Adding a watermark
A watermark is text or an image layered across every page, usually to communicate something about the document's status without altering its actual content — "DRAFT" on a version that isn't final yet, "CONFIDENTIAL" on something that shouldn't be forwarded casually, a company name or logo on a document going out externally. Add Watermark handles this, and it's worth thinking about opacity and placement — a watermark that's too dark or positioned over important text makes the document harder to read, which defeats the purpose if the underlying content still needs to be usable.
Adding page numbers
Page numbers matter more than they seem to until a document doesn't have them — a printed report that gets shuffled, a long PDF where someone on a call says "go to page 12" and you have no way to tell where that is. Add Page Numbers stamps sequential numbers across a document that doesn't already have them, which is common with PDFs generated by combining several source files (see: merging), where none of the originals had numbering built in and the combined result needs it added after the fact.
Cropping margins
Sometimes a PDF has excess white space around the edges — a scan that captured more of the page or table than intended, a document exported with margins wider than necessary for how it's actually being used. Crop PDF trims that down, which is particularly useful when a document is going to be viewed on a small screen and every bit of wasted margin makes the actual content smaller and harder to read, or when a page needs to fit a specific print size and the current margins don't work.
When to reach for the general editor instead
Each of the tools above is built for one specific job, which makes them fast for that job but not the place to go if you need to do several different things to the same document, or if what you actually need is closer to genuine content editing — adding a text box, drawing an annotation, inserting a shape onto a page. Edit PDF is the broader tool for that kind of work, useful when the fix doesn't fit neatly into rotate, watermark, page numbers, or crop, or when you want to make a few different kinds of changes to the same file in one pass rather than running it through several single-purpose tools in sequence.
The short version
Rotate first if a scan came in sideways, use a watermark to mark a document's status without touching its content, add page numbers to anything long enough that referencing a specific page matters, and crop when margins are wasting space. Reach for the general PDF editor when the change doesn't fit one of those specific jobs or you need to make several different kinds of edits at once.