When should you merge PDFs?
Merging is useful when several documents need to be delivered or archived as one file: a cover letter and report, several course notes, or scanned sections of a document. It combines pages into one sequence; it does not rewrite their contents.
A reproducible example
Suppose Cover.pdf has 2 pages, Report.pdf has 5 pages and Appendix.pdf has 3 pages. Open Merge PDF, select the three documents in that order, and select Process & download PDF. The expected result is 10 pages: cover first, report next, appendix last. Always reopen the output and inspect the boundaries between input files.
Before combining
Make copies of your originals. Check that each file can open on its own and that none is password-protected. For page sequences requiring finer control, use Reorder PDF after merging. Very large documents can exceed your device’s browser memory even if each file is below the tool’s upload limit.
What does merging preserve?
The tool copies PDF pages. Page sizes may differ within one merged result. Depending on the source documents, interactive forms, links, attachments, annotations or digital signatures may not remain fully functional. A digitally signed PDF should not be treated as still validly signed after modification without independent verification.
Privacy and troubleshooting
Document bytes are processed in the browser using pdf-lib, which is loaded from a third-party CDN. The site does not implement a document-upload endpoint. If processing fails, try a smaller document, check that each input is a valid PDF, and use the latest browser version. Never put sensitive documents into unrelated services to troubleshoot.
Related tools
Need only a few pages? Use Split PDF. Want to change their order? Use Reorder PDF. Want to remove one page? Use Remove PDF Pages.