Converting PNG to PDF

Where PNG came from, and why it is like this

This conversion does not really change the image — it puts it in a box. A PDF containing a PNG is a document whose single instruction is "draw this image at this position on a page of this size", and the image data inside is essentially the image you started with.

What you gain is everything a document has and an image does not: a defined page size, so it prints predictably; a container that holds multiple images in order as one file; and acceptance by systems that take documents and refuse images. What you gain is not compression, quality, or editability.

Is this conversion lossy?

Mostly not, but the details are worth knowing because a browser-based conversion goes through a canvas.

The image is decoded to pixels and re-encoded when it is embedded, so a PNG that was lossless can be re-encoded lossily on the way into the PDF depending on the format chosen for embedding. For a photograph that is invisible and keeps the PDF a sensible size. For a screenshot of text it can introduce artefacts that were not in the PNG.

Resolution is fixed at whatever the source image had. A PDF made from a 72-DPI screenshot is a 72-DPI document — it will look fine on screen and soft in print, and nothing about the conversion can add detail that was never there.

What happens to metadata, transparency and colour

Transparency does not survive. PDF supports transparency, but the canvas path used here composites the image onto a background first, so a PNG with a transparent background lands on a solid one. If the transparency is doing design work, this conversion will break it.

Metadata does not carry. PNG text chunks and any embedded colour profile are dropped, and the resulting PDF gets its own fresh, empty document metadata. You can set that afterwards with the metadata editor if it matters.

The image does not become text. A PDF made from a screenshot of a document is a picture in a wrapper: not searchable, not selectable, not accessible. This surprises people, because the result looks like a document.

Page size is a decision, not a property of the image. An image with an unusual aspect ratio placed on a fixed page size will be scaled to fit and surrounded by margin.

Why people actually need this

Forms and officialdom, overwhelmingly. Something needs a receipt, an ID, a signed page or a screenshot as proof, and the system accepts PDF only — a very common combination on government portals, expense systems, insurance claims and university submissions. The image exists; it has to become a document.

The second situation is grouping. Several images that belong together — pages of a scanned form, a set of receipts, photographs of a damaged item — need to arrive as one file in a fixed order. PDF is the container everyone can open.

The third is printing. An image sent to a printer prints at whatever size the software guesses; the same image in a PDF prints at the size the page says.

What we measured

This conversion was run end to end before this page was written. Not "should work" — run, with the output checked:

And the ceilings measured for Image to PDF, the tool that performs it, on the hardware described on the limits page:

Not tested

The page also refuses files above 20 MB before it starts, which is a guard written into the tool rather than something the browser imposes. Why those are different.

When something else is the better answer

If the PNG is a screenshot of text and anyone will need to search or copy that text, converting it to PDF does not make it a real document. Run OCR first, or ask for the original file.

If the transparency matters, this conversion will flatten it. Composite the image onto the background you want in an image editor before converting, so you control the colour rather than the converter choosing it.

If the image is a photograph and the resulting PDF needs to be small, compress the image first. Compressing the PDF afterwards works too, but it rasterises the whole page, which is a heavier operation for the same result.