PDF Merger

Joins several PDFs into one, in the order you arrange them. Pages are read out of each source and written into a fresh document with pdf-lib, so the result is a new file rather than a wrapper around the originals. Reorder the inputs before building, because pages are taken strictly in the order the files are listed. Everything happens on your device — contracts, medical records and invoices are never uploaded.

Re-emitting the pages is what makes the output clean and also what it costs. The page content, its fonts and its images come across; the document-level structures do not. Bookmarks and the outline tree are gone, form fields and their values are gone, and the tagging that makes a PDF readable by a screen reader does not survive either — a merged file is less accessible than the documents that went into it, which matters if anyone downstream depends on that. Any digital signature is invalidated as well, not by a flaw in the merge but by definition: a signature attests to a specific byte sequence, and this is a different one.

Password-protected files are refused rather than mangled. The library will open an encrypted document if told to ignore the encryption, but ignoring is not decrypting — the content streams stay encrypted, and saving the result produces a file that no reader can parse, with no error anywhere along the way. This tool checks and stops instead. Remove the password in a PDF reader first, then merge.

Two things to expect in the output. Page size is a property of each page, not of the document, so merging an A4 report with a US Letter invoice gives a single file whose pages are different sizes — correct, and surprising when it prints. And the file will be roughly the sum of its parts rather than smaller: each source brings its own copy of the fonts it embeds, and nothing here recognises that two documents used the same one. If size matters, run the result through a compressor afterwards.