PNG is a lossless image format. PDF is a document container. They overlap because both can carry a single page of an image.
Here is when each is right.
Where PNG wins
Lossless quality, great for screenshots and crisp text-on-image. Transparency support. Smaller than PDFs for very simple images. Standard for the web.
Where PDF wins
Multiple pages. Structured metadata. Signatures and form fields. Professional document standard. If the image is a scanned document, PDF is the expected output.
File size compared
Single-page screenshot: PNG usually smaller. Multi-page scan: PDF smaller because of efficient compression and one container.
Best for…
PNG for screenshots, web images, single-page lossless capture. PDF for scans, multi-page documents and anything that needs structure. Convert-image-to-pdf converts batches.
FAQ
Will the PDF lose PNG quality?
No — PNGs embed losslessly into PDFs if you use a quality-preserving converter.
Can I convert a PDF back to PNG?
Yes — convert-pdf-to-png handles it.
Which is better for OCR?
PDF — it can carry both the image and the OCR text layer.
Screenshots: PNG. Scans: PDF. Switch easily either way.