Converting PDF to JPG turns each page of the document into its own image, so a ten-page file gives you ten pictures. They can be viewed, posted or inserted anywhere an image is accepted. The pages become pixels in the process, so text in the JPG can no longer be selected, searched or edited.
Transfers use HTTPS, and files converted on the free tier are deleted within 24 hours, so the result is not a long-term archive. Quality depends on the source file, so open the JPG file once before you share it.
FromPDFLossless
PDF (Portable Document Format)
A fixed-layout document format created by Adobe and now an ISO standard. A PDF describes pages using vector text, embedded fonts, line art and images, so it prints identically everywhere and its text can be selected, searched and read aloud.
ToJPGLossy
JPEG (Joint Photographic Experts Group)
A compressed raster image format designed for photographs. A JPG is one flat picture with no pages, no text layer and no fonts, which is why it can be viewed, embedded and posted in places where a document file is not allowed.