--- title: How to Build a Browser-Based PDF Signature Tool Using... description: Step-by-step guide to building a browser-based PDF signature tool using vanilla JavaScript, PDF.js, and PDF-lib. Covers uploading and rendering PDFs, creating... canonical: https://daily.dev/posts/how-to-build-a-browser-based-pdf-signature-tool-using-javascript-wshgums5w twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: How to Build a Browser-Based PDF Signature Tool Using JavaScript | daily.dev og:description: Step-by-step guide to building a browser-based PDF signature tool using vanilla JavaScript, PDF.js, and PDF-lib. Covers uploading and rendering PDFs, creating... og:url: https://daily.dev/posts/how-to-build-a-browser-based-pdf-signature-tool-using-javascript-wshgums5w og:image: https://api.daily.dev/og/posts/wsHgUmS5W.png og:image:alt: How to Build a Browser-Based PDF Signature Tool Using JavaScript og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # How to Build a Browser-Based PDF Signature Tool Using JavaScript **[freeCodeCamp](https://daily.dev/sources/freecodecamp)** · [@allinonetools](https://daily.dev/allinonetools) · 35 min read · 4 upvotes · 1 comments ## Summary Step-by-step guide to building a browser-based PDF signature tool using vanilla JavaScript, PDF.js, and PDF-lib. Covers uploading and rendering PDFs, creating signatures via drawing on canvas, typing, or uploading an image, adding text and preset stamps (APPROVED, CONFIDENTIAL, DRAFT, PAID), positioning elements with drag-and-drop, adjusting scale/rotation/opacity, applying elements to specific pages, and generating a downloadable modified PDF entirely client-side. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How do I convert browser canvas coordinates into PDF coordinates when placing a signature with PDF-lib? Calculate scale factors by dividing the PDF page width and height by the rendered canvas width and height (scaleX, scaleY), then multiply the element's browser x/y position by those scales. Because PDF coordinates use a bottom-left origin while the browser uses top-left, subtract the scaled y position and element height from the PDF page height before passing it to drawImage or drawText. _Developers converting screen coordinates to PDF space can save this workflow on daily.dev while building signing tools._ ### What is the difference between an electronic signature and a digital signature in a PDF signing tool? An electronic signature is a visual image (drawn, typed, or uploaded) placed onto a PDF page, similar to inserting a picture of a handwritten signature, with no cryptographic verification involved. A digital signature is certificate-based, using cryptographic keys, trust chains, and validation to verify document integrity and signer identity; simply overlaying a signature image does not create this. _Anyone deciding between visual signing and cryptographic signing can track this distinction on daily.dev._ ### Why does an uploaded JPEG signature image show an unwanted white rectangle when placed on a PDF? A JPEG typically has a solid background because it does not support transparency, so a signature scanned from white paper carries that background into the embedded image, creating a visible box on the PDF page. A transparent PNG only preserves the signature strokes, letting the underlying PDF content show through, which makes PNG the better format for uploaded or canvas-drawn signatures. _Developers debugging signature image artifacts can reference this PNG-versus-JPEG tip on daily.dev._ ## Community discussion Top comments from developers on daily.dev. **@allinonetools** · 1 upvotes > If you build your own PDF tools, I'd love to hear what features you'd add next or any challenges you've faced. Real-world feedback helps shape future tutorials and tools. ## Similar posts on daily.dev - [JavaScript PDF Signature Block: Add and Customize Signatures in PDFs](https://daily.dev/posts/javascript-pdf-signature-block-add-and-customize-signatures-in-pdfs-osa3eaaxi) · Syncfusion · 3 upvotes · 0 comments - [How to Build a Browser-Based PDF to Image Converter Using JavaScript](https://daily.dev/posts/how-to-build-a-browser-based-pdf-to-image-converter-using-javascript-ixeedosyr) · freeCodeCamp · 12 upvotes · 0 comments - [Build a Full‑Featured JavaScript PDF Editor: Annotations, Signatures, and Forms](https://daily.dev/posts/build-a-full-featured-javascript-pdf-editor-annotations-signatures-and-forms-qzwem4yge) · Syncfusion · 8 upvotes · 0 comments - [How to Build a Browser-Based PDF Analyzer Using JavaScript](https://daily.dev/posts/how-to-build-a-browser-based-pdf-analyzer-using-javascript-dhrefkagw) · freeCodeCamp · 3 upvotes · 0 comments - [Why PDF Signing in JavaScript is Hard and How to Make it Easy](https://daily.dev/posts/why-pdf-signing-in-javascript-is-hard-and-how-to-make-it-easy-asnsua9ci) · Syncfusion · 1 upvotes · 0 comments --- Tags: [#javascript](https://daily.dev/tags/javascript) [View this post on daily.dev](https://daily.dev/posts/how-to-build-a-browser-based-pdf-signature-tool-using-javascript-wshgums5w) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"How to Build a Browser-Based PDF Signature Tool Using JavaScript","url":"https://daily.dev/posts/how-to-build-a-browser-based-pdf-signature-tool-using-javascript-wshgums5w","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/how-to-build-a-browser-based-pdf-signature-tool-using-javascript-wshgums5w"},"datePublished":"2026-07-20T23:10:51.982Z","dateModified":"2026-09-14T07:00:23.153Z","description":"Step-by-step guide to building a browser-based PDF signature tool using vanilla JavaScript, PDF.js, and PDF-lib. Covers uploading and rendering PDFs, creating...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/943ec2194646b8dc135ac8b49a75ce58?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/943ec2194646b8dc135ac8b49a75ce58?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"freeCodeCamp","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Person","name":"AllInOneTools","url":"https://daily.dev/allinonetools","image":"https://media.daily.dev/image/upload/s--4ZT8QlF0--/f_auto/v1769790028/avatars/avatar_igzBsWloJeaegzm9bQltZ?_a=BAMAMiiu0","description":"Building Free Online Tools – No Signup, Fast & Privacy-Focused","worksFor":{"@type":"Organization","name":"AllInOneTools","logo":"https://media.daily.dev/image/upload/s--ETjixPd8--/f_auto/v1771310221/companies/allinonetools"},"interactionStatistic":{"@type":"InteractionCounter","interactionType":{"@type":"EndorseAction"},"userInteractionCount":8810}},"commentCount":1,"discussionUrl":"https://daily.dev/posts/how-to-build-a-browser-based-pdf-signature-tool-using-javascript-wshgums5w","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":4},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":1}],"keywords":"javascript","timeRequired":"PT35M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"freeCodeCamp","item":"https://daily.dev/sources/freecodecamp"},{"@type":"ListItem","position":3,"name":"How to Build a Browser-Based PDF Signature Tool Using JavaScript"}]} {"@context":"https://schema.org","@type":"WebPage","@id":"https://daily.dev/posts/how-to-build-a-browser-based-pdf-signature-tool-using-javascript-wshgums5w","comment":[{"@type":"Comment","text":"If you build your own PDF tools, I’d love to hear what features you’d add next or any challenges you’ve faced. Real-world feedback helps shape future tutorials and tools.","datePublished":"2026-07-21T03:13:07.458Z","url":"https://daily.dev/posts/wsHgUmS5W#c-xfzEUvSH5","author":{"@type":"Person","name":"AllInOneTools","url":"https://daily.dev/allinonetools","image":"https://media.daily.dev/image/upload/s--4ZT8QlF0--/f_auto/v1769790028/avatars/avatar_igzBsWloJeaegzm9bQltZ?_a=BAMAMiiu0"},"interactionStatistic":{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":1}}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/how-to-build-a-browser-based-pdf-signature-tool-using-javascript-wshgums5w#faq","mainEntity":[{"@type":"Question","name":"How do I convert browser canvas coordinates into PDF coordinates when placing a signature with PDF-lib?","acceptedAnswer":{"@type":"Answer","text":"Calculate scale factors by dividing the PDF page width and height by the rendered canvas width and height (scaleX, scaleY), then multiply the element's browser x/y position by those scales. Because PDF coordinates use a bottom-left origin while the browser uses top-left, subtract the scaled y position and element height from the PDF page height before passing it to drawImage or drawText. Developers converting screen coordinates to PDF space can save this workflow on daily.dev while building signing tools."}},{"@type":"Question","name":"What is the difference between an electronic signature and a digital signature in a PDF signing tool?","acceptedAnswer":{"@type":"Answer","text":"An electronic signature is a visual image (drawn, typed, or uploaded) placed onto a PDF page, similar to inserting a picture of a handwritten signature, with no cryptographic verification involved. A digital signature is certificate-based, using cryptographic keys, trust chains, and validation to verify document integrity and signer identity; simply overlaying a signature image does not create this. Anyone deciding between visual signing and cryptographic signing can track this distinction on daily.dev."}},{"@type":"Question","name":"Why does an uploaded JPEG signature image show an unwanted white rectangle when placed on a PDF?","acceptedAnswer":{"@type":"Answer","text":"A JPEG typically has a solid background because it does not support transparency, so a signature scanned from white paper carries that background into the embedded image, creating a visible box on the PDF page. A transparent PNG only preserves the signature strokes, letting the underlying PDF content show through, which makes PNG the better format for uploaded or canvas-drawn signatures. Developers debugging signature image artifacts can reference this PNG-versus-JPEG tip on daily.dev."}}]} ```