A step-by-step guide to building a browser-based PDF crop tool using JavaScript and the pdf-lib library. Covers uploading PDFs, rendering page previews, defining crop areas visually, applying crop coordinates to selected pages, generating the cropped PDF, and downloading the result — all without a backend server. Includes code snippets for reading crop coordinates, supporting predefined page ratios (e.g., A4), selecting page ranges, validating inputs, and common mistakes to avoid.
Table of contents
Table of ContentsWhy PDF Cropping Is UsefulHow PDF Cropping WorksProject SetupWhat Library Are We Using?Creating the Upload InterfacePreviewing Uploaded PDF PagesConfiguring Crop SettingsApplying the CropGenerating the Cropped PDFWhy PDF Cropping Is Useful in Real-World DocumentsDemo: How the PDF Crop Tool WorksImportant Notes from Real-World UseCommon Mistakes to AvoidConclusion35.6K Impressions2 Comments