About this tool
Combining separate PDF pages or chapters into a unified document is a standard clerical requirement. Our tool uses direct, client-side browser binary compiling to merge your documents securely.
High-Performance PDF Compiling Logic
Instead of parsing and re-rasterizing pages—which can distort vector lines and degrade font clarity—our client-side merger reads the raw page dictionaries directly from your PDF buffer arrays.
The scaling algorithm handles document page indices systematically:
Where:
- Pmerged is the total index array of the compiled output PDF.
- Pi is the ordered page vector array extracted from input file i.
Because all merging processes execute inside browser memory blocks, your private tax files, contracts, or identification PDFs are never transmitted over external networks.
Frequently asked questions
Everything you need to know about PDF Merger.
How many PDF files can I merge at once?
You can merge up to 20 PDF files in a single operation. Drag and drop them in the desired order, or use the reorder handles to rearrange. The output is a single PDF with all pages concatenated in the order you specify.
Does merging preserve bookmarks, hyperlinks, and form fields?
Hyperlinks within the page content are preserved. Existing document-level bookmarks (outlines) are merged and maintained in the output. Interactive form fields and digital signatures are preserved where the PDF standard allows, though complex XFA-based forms may require revalidation.
Is there a file size limit per PDF?
Individual files up to 100 MB each are supported. The total combined input size should remain under 500 MB for reliable in-browser processing. Very large PDFs (scanned documents with high-DPI images) may take several seconds to merge.
Is my PDF uploaded to a server for merging?
No. Merging uses the pdf-lib JavaScript library, running entirely in your browser. Your PDFs never leave your device. This is critical when merging confidential legal documents, contracts, or financial statements.
Can I reorder pages from different PDFs before merging?
Yes. You can reorder entire documents in the merge queue. Page-level reordering (extracting specific pages from each PDF) is supported via the page range selector — specify which pages from each file to include and in what order.