Merge PDF

Merging copies every page of every file, in the order you set, into one new document. The pages themselves are untouched — same text, same fonts, same resolution — so the merged file is roughly the sum of the originals and nothing is re-compressed on the way through.

What survives a merge is worth knowing, because most tools do not say. Text stays selectable and searchable. Internal links that point within their own file keep working. Bookmarks, form fields and digital signatures generally do not survive — a signature in particular is invalidated by definition, because it certifies a document that no longer exists. If any of that matters, merge first and add the signature to the finished file.