Merge PDF

How to merge PDF files

1. Drop your PDFs onto the upload area or click it to browse; add as many as you need, up to 100 MB in total.
2. Use the up and down arrow buttons to put the PDFs in order.
3. Click "Merge PDFs" and wait a moment while your browser combines the files.
4. Download the merged PDF directly.

Common uses

• Combining multiple chapters or sections into a single document to share with others, use add page numbers after merging for easier navigation
• Merging scanned pages into one file for archiving or submission
• Combining multi-part reports or scanned receipts into a single organised PDF. Compress the merged file to reduce its size before emailing

Technical specification

• Algorithm or formula: Sequential PDF concatenation: pdf-lib copies every page of each source, in the chosen order, into a new PDFDocument. Links inside each source keep pointing at their own pages, and each source's hidden layers stay hidden.
• Browser API or library: pdf-lib for PDF read/write and the page counts shown in the list. Standard File and Blob APIs for input and download.
• Input limits: Up to 100 MB in total across all input PDFs, with no limit on the number of files within that total. Encrypted or unreadable PDFs, and PDFs with no pages, are not added to the list; the tool names each one.
• Output: Single merged PDF (application/pdf) with concatenated pages, downloaded via Blob URL. The file has empty document properties and a new random file ID; comment authors and dates, page-level XMP, and application data are removed.
• Known limitations: Form fields keep their values, but the merged file has no document-level form, so viewers may no longer let you fill them in. Bookmarks, document-level JavaScript, and document-level attachments are not carried over, and embedded multimedia may not work. Page content, images, and text are retained, and so are comment text, form values, attachments on pages, and hidden-layer content.

Frequently asked questions

How many PDFs can I merge at once?

There is no limit on the number of files, only on their combined size: all the PDFs you add can total up to 100 MB. Very large collections may be slow on older devices. All merging happens in your browser using pdf-lib.

Is my PDF uploaded to a server?

All merging is performed in your browser using pdf-lib, a JavaScript PDF library. Our servers are not involved at any point.

Can I reorder the PDFs before merging?

Yes. Use the up and down arrow buttons on each row to set the order. The merged PDF follows the order shown in the list.

Are bookmarks and hyperlinks preserved?

Hyperlinks are preserved: links inside each file still lead to the right pages, and web links keep working. Bookmarks are not carried over. Form fields keep their values, but the merged file has no document-level form, so viewers may no longer let you fill them in. Embedded multimedia may not carry over depending on the source files.