The latest articles on DEV Community by madhav kumar (@madhav_kumar_cc1d644398e0). https://dev.to/madhav_kumar_cc1d644398e0 https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.us-east-2.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F4169863%2F55ee829f-928d-46b8-b083-029588d717cd.jpg https://dev.to/madhav_kumar_cc1d644398e0 en madhav kumar Wed, 07 Oct 2026 21:40:41 +0000 https://dev.to/madhav_kumar_cc1d644398e0/merging-pdfs-in-the-browser-with-pdf-lib-no-server-upload-4a92 https://dev.to/madhav_kumar_cc1d644398e0/merging-pdfs-in-the-browser-with-pdf-lib-no-server-upload-4a92 <p>Most online PDF mergers upload your file to a server. For sensitive documents, that's a problem.</p> <h2> Approach </h2> <p>Use <strong>pdf-lib</strong> in the browser:</p> <ol> <li>Read files with <code>File.arrayBuffer()</code> </li> <li> <code>PDFDocument.load()</code> each source</li> <li> <code>copyPages()</code> into a new <code>PDFDocument</code> </li> <li> <code>save()</code> and download via a Blob URL</li> </ol> <p>The PDF never needs to leave the user's device for this flow.</p> <h2> Verify privacy </h2> <p>Open DevTools → Network, merge a test PDF, and confirm there's no upload request carrying the file body. After the app loads, you can even try offline.</p> <h2> Try it </h2> <p>I packaged this (merge, split, and more) in <strong>PDFCraftify</strong>:</p> <ul> <li>Merge tool: <a href="https://pdfcraftify.com/merge-pdf" rel="noopener noreferrer">https://pdfcraftify.com/merge-pdf</a> </li> <li>Guide: <a href="https://pdfcraftify.com/guides/merge-pdf-without-uploading" rel="noopener noreferrer">https://pdfcraftify.com/guides/merge-pdf-without-uploading</a> </li> </ul> <h2> Tradeoffs </h2> <ul> <li>Browser memory limits very large jobs</li> <li>Password-protected PDFs must be unlocked first</li> <li>Not a replacement for full desktop DTP</li> </ul> <p>If you build similar tools, what edge cases bite you most? Comments welcome.</p> javascript privacy tutorial webdev