A PDF can be turned into images in two main ways: as one image per page, or as a single tall image that contains every page stacked from top to bottom. The stacked approach makes sense when you want to share a short document in a chat, scroll through slides in a single preview, hand over a multi-page reference as one picture, or fit several PDF pages into a place that accepts only one image. The output is a lossless PNG encoded as image/png, which opens anywhere images open, and the conversion runs locally in your browser so the original PDF never leaves your device. Pages of different sizes and orientations keep their original dimensions: the tool picks the widest rendered page as the canvas width, places narrower pages horizontally in the center without stretching, and inserts a configurable white gap between each page so the strip reads cleanly as you scroll. PDF to Long Image is built specifically for that single-tall-image use case, not as a general PDF-to-image conversion.
What "convert a PDF to images" means and where stacking fits
The phrase "convert a PDF to images" covers a few different outputs. Some readers want one image per page so they can drop the files into a photo viewer or a slide deck. Others want a single combined picture that contains every page from top to bottom, which behaves more like a tall screenshot than a folder of files. PDF to Long Image targets the second case: every page is rendered with PDF.js onto its own canvas, those canvases are then stacked into one final canvas, and the result is encoded as one PNG.
This is not the same as the per-page tools on the same site. PDF To PNG produces a separate PNG for every page at lossless quality, and PDF to JPG Converter produces a separate JPG per page at a smaller file size. The long-image route is the right call when the receiving side expects one picture, not when you want to edit individual pages afterward.
When one tall PNG is the right output
The format works well for short documents that you want to share end-to-end without zipping. A ten-page proposal dropped into a chat as one image reads as a continuous strip rather than ten separate thumbnails. A slide deck rendered into one tall picture lets you scrub through the deck the way you would scroll a long screenshot. A scanned reference sheet, a printout of a recipe, a printable worksheet, or a small comic also tend to read better as one strip than as a stack of separate files.
It is the wrong call for documents that need to stay editable. Because the output is a page rendering rather than a structural PDF conversion, the resulting PNG does not preserve selectable text, live links, form controls, layers, or annotations as editable objects. If the text must remain selectable, the PDF to Text Converter is the right tool. If you need editable page-level images, the per-page converters match that task better.
How to stack a PDF into one long image
- Open PDF to Long Image in your browser and choose one PDF file up to 25 MiB from your device. The file never leaves your computer and the rendering libraries only load after you press the convert button.
- Select a rendering scale from the scale control. Scale 1 keeps the page at its native raster size; higher scales multiply both width and height, which sharpens small text in the final image but also makes the combined PNG grow roughly with the square of the scale factor.
- Pick a gap between pages from 0 to 32 pixels. A gap of about 8 to 16 pixels tends to separate pages visually without adding much to the total height.
- Click Convert to Long PNG. The tool preflights every page's scaled viewport and the complete final-canvas layout before it begins encoding, so a too-tall document fails fast instead of producing a truncated image.
- Read the reported combined width, height, and page count. Confirm that the height sits within a comfortable size for the place you plan to share the image.
- Download the resulting PNG. The filename ends with -long.png, the original .pdf suffix is stripped case-insensitively, desktop-unsafe characters are replaced, and the file is a single lossless PNG of the entire strip.
Scale, page gap, and how mixed page sizes are handled
Scale changes the raster dimensions before the pages are combined, so the effect is not linear. A 1500-by-2000-pixel page rendered at 2x becomes a 3000-by-4000-pixel image, and 10 of those pages add up to 10 × 4,000 pixels per page height = 40,000 pixels of combined height. The library behind the rendering is PDF.js, which paints text, vector artwork, photographs, fonts, clipping paths, and other visible page content onto canvases. Increasing scale therefore increases memory, canvas size, and download size together, and small gains in clarity can produce large jumps in final file weight.
Mixed page sizes are the more interesting case. If your PDF has one landscape page and several portrait pages, the converter measures every scaled page first, picks the widest as the canvas width, then drops each page into the strip horizontally centered. Portrait pages sit with white margins on either side rather than stretching to fill the landscape width. The gap area between neighboring pages stays white as well, which keeps the strip readable as you scroll.
Limits on document size and the final canvas
Safety limits keep the operation bounded. The source PDF can be at most 25 MiB and 40 pages. A single rendered page cannot exceed 12,000 pixels on either side or 40 megapixels. All page renders together cannot exceed 100 megapixels. The final combined canvas must also stay within 12,000 pixels per side and 100 megapixels. Because the final image adds gaps and side margins, a long document can hit the height limit even when every individual page is small.
If your document is too tall, drop the scale first. Going from 2x to 1.5x reduces the final height to 75 percent of its original value while keeping the page count the same. Going from 2x to 1x halves the height. When reducing scale still leaves you over the limit, exporting the pages individually with PDF To PNG or PDF to JPG Converter is the practical next step.
Long PNG versus separate page images
The choice between stacked and per-page output is about how the image will be consumed, not about underlying file quality. Both formats start from the same PDF.js page render; the difference is whether the renders are packed into one canvas or saved as separate files.
| Need | Best output | Why |
|---|---|---|
| One scrollable strip of the whole PDF | PDF to Long Image | Single PNG output, no zipping or merging needed |
| Lossless per-page images | PDF To PNG | One PNG saved per page |
| Smaller lossy per-page files | PDF to JPG Converter | JPEG compression keeps download size down |
| Selectable text from the original PDF | PDF to Text Converter | Keeps the text layer editable |
The output filename format also differs by tool. The long-image tool trims any trailing .pdf, replaces desktop-unsafe characters, and ends the file name with -long.png, so a file called Quarterly Brief.pdf becomes Quarterly Brief-long.png.
Errors, encrypted files, and download behavior
The converter rejects encrypted, damaged, unsupported, and over-limit documents with an error rather than producing a partial result. It does not bypass passwords, repair PDFs, verify signatures, or assess whether a document is trustworthy, so any password-protected file must be unlocked before you load it. A newer job always cancels an older one, every per-page canvas is released after it is copied into the final canvas, and the combined canvas plus its download URL are freed when settings change, another file is selected, or the component unmounts. The original PDF is never modified, even after the long PNG is downloaded.