Organize pages
Rearrange, remove and recombine pages without touching what's on them.
Deciding which page tool you need
Almost every page-level job is one of four things: you have several documents and want one, you have one and want several, the pages are in the wrong order, or some of them shouldn't be there at all. Naming which of those you're facing usually settles the tool.
One document out of many is merge. Many out of one is split. Wrong order is reorder, which also drops anything you leave out of the sequence. Unwanted pages are remove pages if there are a few of them, and extract pages if there are more you want gone than kept — naming five keepers beats naming ninety-five casualties.
What page tools deliberately don't touch
Everything in this group works on the structure of a document rather than its contents. Pages are copied whole, keeping their text, fonts, images and dimensions exactly as they were. That's why these operations are lossless and why they run instantly even on large files — nothing is being re-rendered.
If what you need is to change what's on a page rather than which pages exist, that's a different group of tools. Stamping a watermark, adding page numbers or reducing the file size all modify page content, and each says what it costs on its own page.
The order of operations matters
When several of these apply, sequence changes the result. Merge before you number, or each document restarts at one. Remove pages before you number, or the sequence has gaps. Reduce the file size last, after the document is final, because compressing twice from an already-compressed version costs quality for nothing.
One thing that isn't optional: an encrypted document can't be read by any of these tools. The password has to come off in whatever software you normally open the file with, and no tool here can do that for you.