To convert a PDF to an image as one continuous tall PNG, render every page with an in-browser PDF library, draw each rendered page canvas onto a single combined canvas stacked from top to bottom, and encode that final canvas as a lossless image/png — a process that, when done locally, never sends the source document to a server. PDF to Long Image does exactly this: the PDF is opened by the rendering library, every page viewport is calculated, the canvases are stacked onto one final canvas with a configurable gap, and the result is offered as a single PNG download whose filename ends in -long.png.
Unlike a one-page-per-file workflow, this approach produces a single image that scrolls vertically through the entire document. The output is a rasterization of the visible page content: text, vector artwork, photographs, fonts, and clipping paths are painted onto the page canvases by PDF.js, then copied onto the combined canvas. The result is convenient for sharing short documents in a chat where only one image can be attached, for reviewing slides in one continuous scroll, or for placing several PDF pages into a destination that accepts a single picture such as a blog post or a presentation slide.
When one long PNG is the right output
A tall, single-image PNG is not a universal substitute for a PDF or for per-page images. It is the right format in specific situations where one continuous visual strip is genuinely the desired artifact.
- Chat and messaging: Many chat apps accept images but treat multi-file PDFs inconsistently; a single tall PNG stays in one message.
- One-scroll review: Reading slides, comic-style layouts, or sequential diagrams is faster when the pages are already stacked top to bottom.
- Image-only destinations: Forums, social platforms, and CMS fields that accept a single picture can hold a multi-page reference in one image.
- Visual archival: A long PNG preserves the visual order of a short reference document as a flat artifact, useful when the original PDF may be lost or restricted later.
If you need selectable text, live links, form controls, layers, or annotations to remain editable, a long PNG is the wrong format. The output is a painted rasterization; the structural PDF elements are flattened into pixels.
What stays and what does not in the output
Understanding the boundary between preserved and lost content is important before treating a long PNG as a copy of the PDF.
| Preserved in the long PNG | Not preserved |
|---|---|
| Painted text and typography appearance | Selectable / searchable text layer |
| Vector artwork as rasterized pixels | Live links and outline destinations |
| Photographs and embedded raster images | Form fields and widgets |
| Clipping paths and visible page content | Annotations as editable objects |
| Per-page dimensions and orientation | Original embedded images, fonts, and metadata |
Pages can have different widths, heights, and orientations. The tool uses the widest rendered page as the final canvas width and centers every narrower page horizontally inside that width, so a landscape page does not stretch a portrait page to match. The gap you select (0–32 pixels) is painted white along with any side margins, and the entire image is encoded explicitly as lossless PNG via the standard canvas-to-blob path described in the MDN HTMLCanvasElement.toBlob documentation.
Convert a PDF to a long PNG locally
The tool runs the entire pipeline in your browser using PDF.js, the open-source PDF renderer, so the document is never uploaded. Follow these steps to produce the long PNG.
- Open PDF to Long Image and choose one PDF file from your device. The file may be at most 25 MiB and 40 pages.
- Pick a rendering scale. A higher scale increases raster dimensions before pages are combined, which can clarify small content at full size but also raises width, height, memory use, and download size quickly.
- Select the gap between neighboring pages, between 0 and 32 pixels. The gap is painted white.
- Click Convert to Long PNG. The tool preflights every page viewport and the complete combined layout and only then begins encoding. This preflight prevents a single oversized page from leaving a misleading partial result.
- Review the combined width, combined height, and page count shown on the result panel. If those numbers look right for your destination, click the download button to save the single long PNG.
- The downloaded file uses a name based on your input: the trailing .pdf is stripped (case-insensitive), desktop-unsafe characters are replaced, and the suffix becomes -long.png.
The rendering library and shared PDF worker load only after you press Convert, which keeps the initial page light. The fixed worker URL is shared with the other PDF image converters for browser caching, and starting a newer job cancels any older job still running.
Limits that can stop the conversion
Several hard limits guard the operation. If any of them is exceeded, the converter does not produce a partial image; it stops and reports the failure.
| Limit | Value |
|---|---|
| Source file size | 25 MiB maximum |
| Source page count | 40 pages maximum |
| One rendered page | 12,000 px per side and 40 megapixels maximum |
| All rendered pages combined | 100 megapixels maximum |
| Final combined canvas | 12,000 px per side and 100 megapixels maximum |
A long document can reach the height limit even when every individual page is small, because the heights stack. If you see a "too tall" error, reduce the rendering scale, set the gap to 0, or export pages individually instead. The same limits apply to encrypted, damaged, or unsupported PDFs, which the tool reports as errors rather than attempting to repair, sign, or unlock.
Long PNG versus separate page images
A long PNG and a folder of per-page PNGs answer different questions, and the right choice depends on where the image will go next.
- Long PNG is best when the destination accepts one image, the document is short, and a continuous visual strip is genuinely what you want. The encoding is always lossless PNG.
- One PNG per page is the better choice when pages will be reused independently, embedded in different places, or processed by an image editor that struggles with very tall canvases. PDF to PNG creates a lossless PNG per page locally, with exact output dimensions and no upload.
- One JPG per page suits cases where file size matters more than pixel-perfect fidelity. PDF to JPG produces smaller lossy page images at an adjustable quality, also locally.
A very tall PNG can be awkward for printers, email clients that downscale large attachments, image editors with hard canvas caps, and social platforms that re-encode uploads. Treat the long PNG as a specific-purpose artifact, not as a general replacement for the source PDF. The original PDF remains untouched in every case, regardless of which output format you choose.
If you're weighing options, How to Convert PDF to PNG on Windows covers this in detail.