How to Merge Multiple PDF Files and Images in Your Browser
Load Documents
Drag and drop multiple PDFs or photos. The local compiler parses binary headers and renders page thumbnails instantly.
Organize Sequence
Drag pages around to insert attachments, add photo receipts, or correct sequence order before final compilation.
In-Memory Compilation
Click 'Save Merged PDF'. Content streams are unified, font tables consolidated, and the final document generated in milliseconds.
Resolving Cross-Reference (XREF) Collisions Locally
When combining two or more separate PDF documents, the primary architectural hurdle is the cross-reference table (XREF). Each source file has its own internal object numbering scheme (for example, object 14 0 R might be a font dictionary in file A, and an image stream in file B).
PDFListo performs zero-network indirect ID remapping in volatile RAM: it assigns a clean unified index space without duplicating identical embedded font subsets. If you add raster images (JPEG, PNG, WebP), the engine dynamically crafts standardized page containers without destructive transcoding.
Frequently Asked Questions about Merging PDFs
No arbitrary limits are imposed. Because execution occurs entirely inside your web browser via JavaScript TypedArrays, capacity is dictated only by your device's available RAM.
Yes. Destination offsets and outline trees are recalculated to ensure page jumps and table of contents remain accurate in the merged file.