Is this tool really free?

Yes, all our PDF tools are completely free to use with no hidden costs, subscriptions, or per-file charges. We support the service through non-intrusive advertising, not by charging for basic document operations. You can use any tool as many times as you like, with no daily limits, file size restrictions, or account requirements whatsoever.

Absolutely. All PDF processing happens directly in your browser using local JavaScript and WebAssembly libraries. Your files are never uploaded to any server, never stored in the cloud, and never transmitted over the internet. The files remain entirely on your device from start to finish, giving you complete control over your sensitive and confidential documents.

What is page interleaving?

Page interleaving merges two PDF documents by alternating their pages — placing page 1 from document A, then page 1 from document B, then page 2 from A, then page 2 from B, and so on. This produces a single document where content from both sources alternates throughout. The primary use case is reassembling double-sided scans that were captured with separate front and back passes.

When would I need to interleave?

Interleaving is most commonly needed when scanning a double-sided document without a duplex scanner. You scan all the odd-numbered (front) pages first, creating one PDF, then flip the stack and scan all the even-numbered (back) pages, creating a second PDF. Interleaving combines these two PDFs back into the correct reading order with fronts and backs properly paired.

What if the two PDFs have different page counts?

When the two PDFs have different numbers of pages, the tool interleaves the pages for as long as both documents have content, then appends the remaining pages from the longer document at the end. This handles cases where the back-side PDF has fewer pages due to the last sheet being single-sided or the scanning capturing a different number of pages.

Can I interleave in reverse order?

Yes, you can set the interleaving order to accommodate different scanning situations. If you scanned the back pages in reverse order (a common occurrence when flipping the paper stack), choose the reverse mode which reverses the second PDF's page order before interleaving. This correctly pairs the back of page N with the front of page N regardless of which direction the backs were scanned.

Can I interleave more than two PDFs?

The interleave tool is designed for combining two documents by alternating their pages. For more complex interleaving patterns involving three or more documents, you would need to interleave two documents at a time in multiple passes. Alternatively, the Page Organizer tool gives you full manual control over page order, allowing any arbitrary interleaving arrangement.

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