OptiDrop

Combine Multiple PDFs — Free Online Tool

Upload multiple PDFs, reorder them by dragging, choose append or interleave mode, and download a single combined PDF. Everything runs in your browser.

Click or drag PDF files here

Upload two or more PDF files to combine

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Combine Multiple PDFs — Merge PDF Files Online

Easily combine two or more PDF documents into a single file. Upload your PDFs, drag to reorder, choose between append mode (sequential) or interleave mode (alternating pages), and download the merged result instantly.

Append vs Interleave Mode

Append mode is the standard merge: all pages from the first PDF, followed by all pages from the second, and so on. This is ideal for combining chapters, sections, or separate documents into one continuous file.

Interleave mode alternates pages between files: page 1 from PDF A, page 1 from PDF B, page 2 from PDF A, page 2 from PDF B, etc. This is perfect for combining front-and-back scans, or merging odd/even page exports into one document.

100% Private — Files Never Leave Your Browser

All processing uses the pdf-lib library running entirely in your browser. No file is ever uploaded to any server, guaranteeing your documents remain private and secure.

Frequently Asked Questions

Append mode adds all pages from each PDF in order (all of A, then all of B). Interleave mode alternates pages (A1, B1, A2, B2...), which is useful for combining front and back scans.
You can combine as many PDFs as you need. There is no hard limit, though very large files may take longer to process in the browser.
No, all processing happens entirely in your browser using the pdf-lib library. Your files are never uploaded anywhere, ensuring complete privacy.
Yes, you can drag and drop the PDF file cards to rearrange them in any order before combining.

Last updated: June 2026