How a PDF page becomes a picture
Unlike the other PDF tools here, which edit page structure with pdf-lib, this one uses Mozilla's pdf.js (pdfjs-dist) to render each page. For every page it asks for a viewport at your chosen scale, creates a canvas of that size, lets pdf.js paint the page on it, and exports the canvas as JPG or PNG. Vector text and graphics are rasterized into pixels at that moment, so the result can no longer be searched or selected.
Resolution is set in DPI
A PDF page is measured in points, at 72 per inch. The tool converts your chosen DPI to a render scale of DPI divided by 72, so 300 DPI renders at a scale of about 4.17 and a Letter page really comes out at 300 pixels per inch. The four options are 96 (screen), 150 (standard), 200 (high) and 300 (print) DPI.
| Option | Render scale | Letter page (612 x 792 pt) | Approx. pixel memory per page |
|---|---|---|---|
| Screen (96 DPI) | 1.33x | 816 x 1056 px | 3.3 MB |
| Standard (150 DPI) | 2.08x | 1275 x 1650 px | 8.0 MB |
| High (200 DPI) | 2.78x | 1700 x 2200 px | 14.3 MB |
| Print (300 DPI) | 4.17x | 2550 x 3300 px | 32.1 MB |
The memory figure is width x height x 4 bytes of canvas pixels (RGBA), computed before compression. It explains why a 200-page PDF at 300 DPI can stall a phone: pages are rendered one after another and each page is drawn on a temporary canvas, and the finished images stay in memory until you convert again or leave the page.
JPG or PNG
For JPG the canvas is first filled with white, then the page is drawn, and the quality slider runs from 30 to 100 percent (default 85). PNG ignores the slider and is lossless, giving larger files. Choose PNG for slides and pages with thin lines or small text, where JPG leaves fuzzy halos, and JPG for scanned pages and photographs.
Results and limits
- You can download pages one by one, all in sequence (one download per page, 150 ms apart), or as a single
.zip. Files are named likereport-page-3.jpg. - Leave the "Pages" box blank to convert every page, or enter a selection such as
1-3, 5to convert only those pages. Files keep the original page number in their name, for examplereport-page-5.jpg. Numbers outside the document are ignored, and if none are valid you get a message instead of an empty result. - PDFs that need a password to open fail with "Could not render this PDF". Files with only a permissions (owner) password usually render fine.
- A very large page, such as an A0 poster at 300 DPI, can exceed the browser's maximum canvas size (about 16,384 pixels per side or 100 megapixels). The tool checks this before drawing and tells you which page is too big, so you can pick a lower resolution and convert again.
To go the other way and turn images back into a document, use Image to PDF.