Quick guide
Merge PDFs free: append files or alternate scan pages
Merge PDFs in two ways: append every page in queue order, or alternate pages from two scanned PDFs. It works for applications, reports, receipts and front/back scan sets. PDF content stays on your device and is never sent to the VPS for merging.
What this tool does
- Append up to 50 PDFs, 200 MB total and 500 pages.
- Alternate pages from two PDFs and reverse the second file for back-side scan sets when needed.
- Reorder documents, name the result and stop without creating a partial file.
- Append mode reads one file at a time. Alternate mode holds both PDFs in device RAM. Neither mode uploads document content to the VPS.
How to use Merge PDF
- 1Choose at least two PDFs and check that they are not damaged or password protected.
- 2Choose append in queue order, or alternate when you have two scanned PDFs, then decide whether the second file should be reversed.
- 3Check the queue order, name the output, merge, and open the new PDF to inspect every page before sharing it.
Frequently asked questions
How many PDFs can I merge and what are the limits?
Append mode supports up to 50 files per run, 200 MB total and 500 pages. Alternate-pages mode requires exactly two PDFs.
How are pages ordered in append mode?
All pages from the first file come first, followed by every page from each subsequent file in the top-to-bottom queue. Use the arrow buttons to reorder files before merging.
How does alternating pages from two PDFs work?
The tool takes page 1 from the first PDF, page 1 from the second, then page 2 from each. If page counts differ, the remaining pages from the longer file are appended and never discarded.
When should I reverse the second PDF?
Reverse the second file when you scanned all front sides first, then flipped the paper stack so the back-side PDF runs in reverse order. Always inspect the result because scanner feed directions differ.
Can I merge a password-protected or damaged PDF?
No. Remove protection with the correct password first. If a file cannot be read, the tool identifies its queue position and creates no partial result.
Will bookmarks, forms or digital signatures remain unchanged?
Always inspect the result. Copying pages does not guarantee that document-level structures such as bookmarks, form fields, attachments or digital signatures will still work or validate as they did in the source.
Does merging use VPS resources?
No. The browser merges documents with the user device CPU and RAM. The VPS only serves the page, scripts and libraries. Append mode reads one file at a time, while alternate mode holds both PDFs in device memory together.
Reference: copying PDF pages with pdf-lib: undefined