Embed any PDF on any website.

PDF.js is the JavaScript-based PDF rendering engine Mozilla built for Firefox in 2011. It is the same viewer that ships natively in Firefox today, and it is the engine behind most production-grade web PDF embeds, including Wikipedia, Internet Archive, and the U.S. Government Publishing Office. PDF.js renders each page to a canvas while overlaying a transparent text-layer that supports selection, copy, search, and screen-reader access. It handles forms, annotations, embedded fonts, attachments, and most encryption modes. The trade-off is bundle size: the full viewer plus worker is around 560 KB gzipped, which is significant for a single feature on a single page. Poper solves this by lazy-loading PDF.js only when the viewer scrolls into the viewport, and by offering a native-viewer fallback mode for cases where 560 KB is too much budget to spend. PDF.js is BSD-2-Clause licensed and used in production by hundreds of thousands of sites, which means it is battle-tested across every browser, every PDF version, and most of the weird edge cases you encounter with PDFs in the wild (oversized scans, broken metadata, embedded subsetted fonts, mixed text and image content).

Embedded PDFs have a deserved reputation for being terrible on mobile. The default behavior of an <iframe src='document.pdf'> on iOS Safari is to display the first page at viewport-fit width, then refuse to scroll beyond it. Android Chrome typically shows a download prompt instead of inline rendering. Pinch-zoom is broken inside iframes by default because the embedded content does not receive the gesture. The reading experience is so bad that many sites just give up and link to the PDF instead, losing the visitor to a separate browser tab. The Poper widget fixes this with three changes: it detects touch devices and binds pointer events to the canvas layer so pinch-zoom and pan gestures work; it sets a sensible default zoom (fit-to-width) instead of fit-to-page so 12-point body text is readable without zooming; and on Android Chrome where inline rendering is unreliable, it falls back to PDF.js client-side rendering instead of the failing native handoff. The net result: a PDF embedded with Poper is actually readable on a phone, which sounds like a low bar, but the bar most embed solutions clear is below it.

PDFs are notorious for accessibility failures. A scanned PDF with no OCR is just an image and is invisible to screen readers. Even text-based PDFs are inaccessible by default unless the source document includes structural tags (heading levels, lists, tables, reading order, alt text on images, language declarations). WCAG 2.1 Level AA, which most jurisdictions reference (EU EN 301 549, U.S. Section 508, UK PSBAR), requires that PDFs published on a public website be tagged. The catch: many PDF embed solutions strip or ignore those tags during rendering, breaking the accessibility chain even when the source PDF is properly tagged. Poper preserves the full PDF tag tree through PDF.js, exposing it to assistive technology via standard ARIA attributes on the text-layer. Screen readers (JAWS, NVDA, VoiceOver, TalkBack) can navigate the document by heading, jump between tables, and read alt text on figures. If your source PDF is not tagged (you can check with Adobe Acrobat's Accessibility Checker, or pdfa-validate, or veraPDF), Poper still preserves what is there, but no widget can tag a PDF that was not tagged at source. The right place to fix accessibility is in the document, not in the embed; widgets that claim to 'add accessibility' are at best providing visual zoom features, not real WCAG conformance.

Before you embed a PDF, ask whether PDF is actually the right format for your content. PDFs were designed for print: fixed page size, fixed layout, fonts embedded, intended to look identical on every screen and every printer. That is exactly the wrong design constraint for a website, where the screen is variable, the input device is unknown, and the visitor scrolls instead of paging. For long-form content like blog posts, documentation, knowledge base articles, and product copy, native HTML beats embedded PDF on every metric: lower bundle, faster paint, better mobile UX, full accessibility, indexable by search engines, linkable to specific sections. PDF only wins when fixed layout is genuinely required: signed legal contracts, regulatory filings, tax forms, scientific papers with fixed pagination for citation, print-bound brochures, menus where the design is the point. For documents that fall between (ebooks, lookbooks, magazines, catalogs), a flipbook widget often beats both raw PDF embed and HTML conversion: the page-turning interaction signals 'magazine' rather than 'document', engagement metrics typically beat PDF by 3-5x, and Poper's flipbook widget can ingest your existing PDF as input. Pick the format based on what the visitor will do with the content, not on what file you happen to have lying around.

Adobe offers the PDF Embed API as a free service, which sounds great until you read the fine print. The viewer is hosted on Adobe's CDN and renders inside an iframe loaded from documentcloud.adobe.com. That has three downstream consequences. First, the toolbar shows the Adobe logo and 'Powered by Adobe' branding, which is fine if you are Adobe but distracting if you are anyone else. Second, the iframe is a third-party domain in browser tracking-prevention reports, which means tools like Brave's tracker count, Apple's Privacy Report, and Firefox's Enhanced Tracking Protection all flag your page as embedding Adobe trackers, even though the use case is benign. Third, the API has rate limits and a terms of service that reserves Adobe's right to add advertising, change branding, or shut down free tier access at any time; multiple Adobe APIs have been deprecated or commercialized over the years, so betting your site's PDF rendering on Adobe's continued generosity is a real risk. The open-source path (PDF.js + your own CDN, which is what Poper provides) avoids all three problems: no third-party branding, no third-party domain in tracker reports, no API key, no terms of service that can change. The trade-off is that you maintain the bundle, but Mozilla maintains PDF.js for Firefox itself, so the upstream is healthy. For 95% of use cases, the open-source path is the right answer.