Converting PDF pages to JPG

Where PDF came from, and why it is like this

A PDF is a set of drawing instructions, not a picture. A page saying "draw this text in Helvetica at this position, then this vector logo, then this photograph" is stored as those instructions, which is why the text stays sharp at any zoom level and why the file can be small even at high quality.

Converting to JPG throws that away and executes the instructions once, at one fixed resolution, producing a flat grid of pixels. Everything that made the PDF resolution-independent is spent at that moment. This is not a flaw in the conversion — it is what "convert to an image" means — but it is the fact that determines whether the result is useful.

Is this conversion lossy?

Irreversibly, in two ways at once.

The first is the text layer. After conversion the words are pixels: not selectable, not searchable, not readable by a screen reader, and not extractable without running OCR over the result. A PDF that was perfectly accessible becomes an image that is not.

The second is resolution. The rendering happens at a chosen scale, and detail finer than that scale is gone. Text that looked crisp in the PDF can look soft in the JPG, particularly at small point sizes, because the renderer had to decide which pixels a thin stroke covers. Then JPEG compression adds its own artefacts on top, and JPEG is at its worst on exactly this content — sharp black text on white is the pattern its 8×8 blocks handle least well.

What happens to metadata, transparency and colour

Nothing carries over. A PDF's document metadata — title, author, producer, creation date — has nowhere to go in a JPEG produced from a canvas, and none of it is written. Neither are bookmarks, annotations, form fields, links or attachments. What survives is the visual appearance of the page and nothing else.

Vector art becomes pixels. Logos and diagrams drawn as vectors were resolution-independent and now are not. Enlarging the JPG afterwards will show the pixels, where enlarging the PDF would not have.

Transparency flattens. PDF pages can contain transparency and JPEG cannot store it, so anything transparent is composited onto the page background during rendering.

Multi-page documents become multiple files. A JPEG holds one image, so a document becomes one file per page, delivered as a ZIP.

Why people actually need this

Usually somewhere that will not take a PDF. Social media is the clearest case — most platforms accept images and not documents, so a poster, a menu or a certificate laid out in a PDF has to become an image before it can be posted. Marketplace listings, messaging apps and a lot of web forms behave the same way.

The second situation is embedding. Putting a PDF page into a slide deck, a document or a web page is awkward; putting a JPG in is trivial. People convert because the image is going to be placed inside something else, where its lack of a text layer costs nothing.

The third is a preview or thumbnail — one image standing in for a document in a listing or an email.

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 PDF to JPG, the tool that performs it, on the hardware described on the limits page:

Not tested

The page also refuses files above 100 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 anyone will ever need to select, search or copy the text, do not do this. The conversion is one-way and recovering the text afterwards means running OCR on the images, which is slower and less accurate than the text that was there to begin with.

If the goal is a smaller PDF rather than an image, the compressor is the tool — though note from its entry on the limits page that it works by rasterising pages too, so it has the same effect on the text layer.

If the goal is fewer pages rather than pictures, splitting or reordering keeps the document a document.

If the destination accepts PNG, prefer it: text and line art survive rasterising much better without JPEG's artefacts on top.