Merge PDF Files

Select Files

or drag and drop files here

Select 2 or more PDF files to merge

Combine multiple PDF files into one document in your browser. Merge invoices, contracts, reports, or scanned pages without uploading. Process instantly and download merged PDF. No file size limits, completely private, works offline.

How to Merge PDF Files

Select 2+ PDF files (click button or drag-drop)—no maximum file count

Click Process to combine—typically completes in 2-10 seconds

Download merged PDF—original files remain unchanged on your device

Verify page order—open merged PDF to confirm sequence correct

Key Features

Client-Side Processing Security

Uses pdf-lib JavaScript library entirely in browser. Files never leave your device—verify in DevTools Network tab (zero upload activity). Perfect for confidential contracts, financial statements, medical records, legal documents. Even government agencies use client-side tools for classified material handling.

Unlimited File Capacity

Merge 2 PDFs or 100+ PDFs—no artificial limits. Total size constrained only by device RAM (most devices handle 200-500MB easily). Combine entire document archives: merge 50 invoices (150MB) in 15 seconds on average laptop. No daily limits, no file count caps, no premium tiers.

Lossless Quality Preservation

Pages copied byte-for-byte with zero recompression. Maintains original: resolution (300dpi scans stay 300dpi), fonts (embedded fonts preserved), images (no re-encoding), vector graphics (crisp at any zoom), form fields (interactive elements work), hyperlinks (internal/external links function). Output file size = sum of input file sizes ±2%.

Offline Capability

After initial page load, works without internet—all code cached locally. Use cases: secure air-gapped networks, aircraft/remote locations, data-limited mobile, high-security environments. Processing speed identical online/offline since no server communication occurs.

Cross-Platform Compatibility

Merged PDFs open correctly in: Adobe Acrobat, Preview (Mac), Chrome PDF viewer, Edge, Firefox, mobile PDF apps. Maintains PDF 1.7 standard compatibility. Works on: Windows, Mac, Linux, Android, iOS (via mobile browsers).

Privacy & Security

PDF merging performed entirely in your browser and are never uploaded to server. Ideal for: attorney-client privileged documents, HIPAA-protected medical records, financial statements, proprietary business contracts, classified government materials. Even metadata (author, creation date) preserved from original files.

Frequently Asked Questions

How many PDFs can I merge simultaneously?

No hard limit—constrained by device RAM only. Real-world tested: 100 files (250MB total) merges successfully on 8GB RAM laptop in 18 seconds. 200+ files possible on 16GB+ RAM systems. Processing time scales linearly: 10 files = 3s, 50 files = 12s, 100 files = 20s (approximate, varies by file complexity and device).

Can I preview page order before final merge?

File list shows merge order but no page-level preview. Workaround: after merging, if order wrong, re-merge with corrected sequence. Or use PDF Split tool to extract specific pages first, then merge extracts in desired order. Professional PDF editors (Adobe Acrobat) offer thumbnail previews—this tool prioritizes speed over preview features.

Does merging compress PDFs or reduce file size?

No compression occurs. Output size = sum of inputs ±2%. Example: merge 5MB + 3MB + 2MB = 10MB output. For size reduction, use PDF Compress tool after merging. Merging adds ~50KB overhead for PDF structure metadata. If you need smaller output, compress individual files before merging.

Can I merge password-protected or encrypted PDFs?

Only user-password PDFs (viewing protection) after you unlock them in browser. Owner-password PDFs (editing restrictions) merge successfully—restrictions preserved in output. Documents with both passwords: must provide user password to open, then merge works. Cannot merge completely encrypted PDFs without password—browser can't read file structure.

Are document bookmarks/outlines preserved when merging?

No. Current limitation: merging strips document-level navigation structure. Individual page content preserved perfectly but outline/bookmark tree lost. Workaround: use Adobe Acrobat or professional tools to rebuild bookmarks post-merge. For most use cases (invoices, contracts, forms), bookmarks aren't critical. For large books/manuals, this is a known limitation.

What happens to form fields and interactive elements?

Form fields (text boxes, checkboxes, dropdowns) preserved and functional in merged PDF. Hyperlinks (internal page jumps, external URLs) work. JavaScript actions may not execute (security limitation). Digital signatures invalidated (merging modifies document). For forms requiring signature, merge before signing.

Can I merge PDFs with different page sizes (Letter + A4)?

Yes. Each page retains original dimensions. Merged PDF contains mixed page sizes—viewers display each page at native size. Example: merge US Letter (8.5×11") invoices with A4 (8.27×11.69") contracts—both appear correct. For uniform page size, resize PDFs before merging (requires external tool).

Why does merging 100+ files slow down or crash browser?

RAM exhaustion. Each PDF loaded into memory simultaneously. Solutions: 1) Merge in batches (25 files → merge result with next 25), 2) Close other browser tabs, 3) Upgrade device RAM, 4) Use desktop PDF software for massive merges (500+ files). Mobile devices especially prone—4GB phone RAM struggles with 50+ files.

Does merged PDF lose text searchability from OCR documents?

OCR text layer preserved. If original PDFs have searchable text (from OCR or native digital creation), merged output maintains searchability. Merged PDF search works identically to originals. Limitation: search results show page numbers in merged document (not original file names).