Markr
A free, browser-based PDF annotation tool. No installation, no sign-up. Just upload, annotate, and download.
The problem
PDF annotation is inaccessible
Most people who need to annotate a PDF just need to fill in a form, highlight text, add a quick note. Something so simple and commonplace should not require a subscription to Adobe or a one time payment to other software options.
For students, professionals, and anyone who just needs to mark up a document quickly, none of these options make sense. The tool should get out of the way and let you do the work.
The solution
Browser-based, free, no strings attached
Markr is built around one principle: the fewest possible steps between a user and an annotated PDF. Open the site, upload your document, annotate it, download the result. No account. No installation. No cost.
The entire tool runs in the browser using PDF.js for rendering and a custom annotation layer built in vanilla JavaScript. Hosting on Firebase keeps it fast globally and costs essentially nothing to run at scale.
Key features
What Markr can do
Tech stack
Built lean
No framework overhead. Markr is built entirely in vanilla JavaScript which means it is fast to load, simple to maintain, and proof that a useful product doesn't need a complex stack behind it. Markr simply creates a canvas over existing PDFs which allows for simple annotation and then creates a new PDF with the canvas over the top of the original PDF.
Outcome
A tool that does one thing well
Markr is live at markr-pdf.web.app and growing organically through search traffic. It's monetised and supported by users through BuyMeACoffee which allows for covering hosting costs without charging users directly.
Markr started as a solution to a personal frustration and became one of Interactive 63's most visited products. It demonstrates what's possible when a tool is built with a single clear purpose and no unnecessary complexity.
Want something built for you?
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