pdf to png with transparent background

Technically, the PNG export uses a canvas rendering context created with alpha transparency enabled, and skips filling any background color before rendering the PDF page onto it. Whatever transparency exists in the source page's rendered output carries through into the exported PNG file. The JPG export, by contrast, always fills white first, because JPG has no transparency channel to preserve — even if the source had transparent areas, the JPG version would show them as solid white.

This matters specifically for PDFs that were generated with intentional transparency — for example, a logo or graphic element exported from design software as a PDF, where the areas outside the actual artwork are meant to stay transparent rather than white, so the image can be placed over different colored backgrounds elsewhere.

For a typical scanned document, form, or text-based PDF, this distinction won't be visible, since those pages are rendered as fully opaque content covering the whole page — there's no transparent region for the PNG format's transparency support to actually preserve.

If you're not sure whether your specific PDF has transparent regions, export it as PNG and open the result in an image viewer or editor that shows a checkerboard pattern behind transparent areas (most do) — if you see a checkerboard anywhere, that confirms genuine transparency was preserved from the source.