PNG to PDF converter

What the PDF actually contains

The engine decodes your PNG with the browser's image decoder, splits it into an RGB colour array and an alpha array, and hands both to pdf-lib. The alpha channel becomes a separate PDF SMask object, so transparent and semi-transparent pixels stay transparent when a viewer opens the PDF — they are not flattened onto white the way a JPG conversion would do.

Colour data is stored as an 8-bit DeviceRGB image object compressed with the standard deflate filter. Deflate is lossless: no JPEG-style block artefacts are introduced, and the pixels you see in the PDF are the pixels you supplied. The page itself is created at the image's pixel dimensions, treated as points, and the image is drawn across the whole page.

• One input PNG produces one PDF with exactly one page — files are not merged into a multi-page document
• Alpha is preserved as a PDF SMask rather than flattened
• Pixel data is re-encoded losslessly, never re-compressed with JPEG
• The output is named after your original file with a .pdf extension and downloaded from your browser

Why the page is the image size

The default page preset is Fit: the page measures the same numbers as the image, in points. A 1200×800 PNG becomes a 1200×800 pt page with the image filling it edge to edge. That keeps the PDF a faithful container rather than a document with margins and whitespace you did not ask for.

If you need a printable sheet instead, choose A4. The page becomes 595×842 pt, the image is scaled down to fit inside 24 pt margins and centred, and the surrounding area stays white. A portrait PNG fills the height; a landscape PNG fills the width and leaves bands above and below.

When PNG to PDF is the right move

PDF is the format that survives being emailed, printed and archived. A PNG pasted into a report can be resized by the document editor, cropped by a mail client or resaved by a viewer; a PDF page pins the geometry, so what you send is what gets printed.

This is useful for scanned receipts and documents exported as PNG, screenshots that must sit inside a printed specification, charts with crisp lines, and logos placed on a letterhead. Because the PNG is embedded losslessly, thin rules and text in a screenshot stay sharp — unlike a route that converts the PNG to JPG first and then wraps that JPG in a PDF.

• Print-ready single sheets: screenshots, scans, receipts, certificates
• Charts and diagrams where line sharpness matters
• Assets with transparency that must stay transparent in a viewer
• Archival copies where you want a fixed page size rather than raw pixels

File size, honestly

A PDF wrapper is usually a little larger than the PNG it came from, because the image is stored as uncompressed RGBA plus a mask and then deflated, rather than reusing PNG's own compressed stream. Expect a comparable size, sometimes larger for photographic PNGs. If your goal is a smaller file, PDF is the wrong target — convert to WebP or JPG instead and keep the PDF only when the container itself is the requirement.

Options and limits

Settings offers one real option: Page, Fit or A4. There is no margin, rotation, DPI or multi-file merge control, because the engine does not implement them; each dropped file is converted on its own and returns its own PDF. Each dropped file is converted on its own and returns its own PDF.

The engine rejects an empty file, a file larger than 20 MB, and an image above about 40 megapixels. Animated PNGs decode as their first frame only — animation is not carried into the PDF. Colour profiles and text metadata such as EXIF tags are not transferred; the PDF carries the pixel grid and nothing else.

• One file per run (the picker converts a single image), each up to 20 MB
• Images above about 40 megapixels are refused
• Animated PNG becomes a single still page
• Metadata and colour profiles are not preserved

How the conversion runs

The file is read from your disk into memory, decoded by the browser, assembled into a PDF document by pdf-lib and saved back as a Blob — all inside this tab. No image is uploaded and nothing is stored after you close the page. The vendor pdf-lib bundle is loaded from this site's own assets only when a PDF conversion is requested, and an abort during a batch stops the run instead of producing a half-written file.

This route is beta: it is tested against generated PNG fixtures for page count, page dimensions, embedded image objects and mask presence, but real-world PNGs vary. Check the first PDF in your own viewer before converting a batch.

• Runs entirely in the browser; no server round trip
• Abort stops the batch cleanly
• Beta status: verified on fixtures, not on every PNG variant

Questions