Put files together, or take them apart

A PDF is a container: a page tree pointing at page objects, each carrying the fonts, images and vector drawings that page needs. Merging copies those page objects into a new container in the order you choose. Splitting copies subsets of them into several new containers. Neither operation re-draws anything, so a merged or split document is exactly as sharp as the file it came from and its text is still selectable, searchable and readable aloud.

Both tools take ranges, and that is usually the shortcut. Merge can take pages 2 to 5 of one document and all of another in a single operation, which saves a split followed by a merge. Split treats each range you write as its own output file, so 1-3, 4-8 gives two documents rather than one document of eight pages — and it shows you the exact list of files before it builds any of them.

The document's metadata does not travel at all: a merged or split file has no title, author, producer or timestamp, not even from the first source. That is deliberate, because a bundle that quietly inherits one source's author is a small privacy leak nobody asked for. These tools do not accept an encrypted PDF as a merge or split source, so take the password off it with the unlock tool first — that tool needs the password the file opens with, and proves the copy it makes really opens without one. The tool names that boundary rather than failing vaguely. The archive tools make and open ordinary ZIP files with Deflate compression; they intentionally do not implement RAR, 7z or encrypted ZIP. For a PDF-specific password mode, the protection tool writes AES-128 revision 4 and reports its finished-file read-back checks.