A PDF looks blurry when the pictures inside it are printed larger than their pixels allow. This tool lists every image in the document with the resolution it is actually drawn at, lets you pick the ones that need help, upscales them with a real model on your own GPU, and puts them back. Text stays text: only the image objects are replaced.
How it works
- Drop a PDF. Every embedded image is listed with its size, its page, and the effective DPI it is drawn at — the low-resolution ones are ticked for you.
- Choose the scale and quality tier, then upscale. Compare any result against the original before you commit.
- Download the PDF. Same pages, same text, sharper pictures.
Questions
- Does my file get uploaded?
- No. The models and all processing run inside your browser on your own device. You can verify this yourself: open your browser’s DevTools, watch the Network tab, and process a file: there are no uploads. After the first visit most tools also work fully offline.
- How is this different from upscaling the whole PDF?
- Dropping a PDF on the image upscaler rasterises every page — the text becomes pixels, and the file stops being searchable or selectable. This tool swaps the image objects only, so headings, body text, links and vector drawings are untouched and the document still behaves like a document.
- Which images can it not handle?
- Stencil masks (1-bit shapes painted in a fill colour) are listed but not offered: there is no photograph there to improve. Anything the browser and pdf.js together cannot decode is listed with the reason and left alone rather than silently skipped.
- Will the file get bigger?
- Yes, and usually by a lot: four times the pixels is roughly four times the image data, and the upscaled images are stored as PNG. The tool reports the finished size before you download so it is never a surprise.
- Does it need a fast machine?
- The best tier is Real-ESRGAN running tile by tile on your GPU — tens of seconds per image is normal, and a big scan can take longer. The two faster tiers are instant and still sharper than a plain stretch. WebGPU is required for all three.