How does a PDF merger work?

A PDF merger copies pages from multiple source documents into one new PDF in the selected file order. It is useful for combining scans, reports, forms, or document sections without printing and rescanning or uploading the files to a remote conversion service.

Pdf-lib performs the page copying entirely in the browser, leaving original files unchanged. Encrypted, malformed, signed, or very large documents may fail, and creating a new combined file can invalidate assumptions tied to original digital signatures, forms, outlines, attachments, or document-level metadata.