Add protective binding margins and gutter spacing to PDF documents directly in your web browser. Standard letter and A4 documents designed in word processors or design software frequently lack adequate inner margin clearance, causing 3-ring binder hole punches, comb teeth, or spiral wires to clip through headings, text columns, or technical schematics.

This tool utilizes the client-side pdf-lib library to expand each page canvas by your selected gutter allowance (such as 0.75 inches or 54 points) without downscaling or distorting your original content. In duplex mode, the tool automatically alternates the gutter offset across facing pages: odd pages shift rightward to protect the left-hand binding edge, while even pages shift leftward to protect the right-hand margin when printed double-sided.

For example, loading a 20-page employee manual with a 0.75-inch gutter in duplex mode expands the page canvas from 612×792 points to 666×792 points, placing odd pages at an x-offset of 54 points and even pages flush left, leaving clean clearance for physical punching.

All page rendering, canvas expansion, and PDF compilation execute locally on your machine using browser WebAssembly and JavaScript. No confidential reports, forms, or documents are uploaded to any external server.