Render the pages of a PDF as image files. Choose PNG or JPG and the resolution in DPI, and export the whole document or a single page. Useful when you need a page as a picture - to drop into a slide deck, post somewhere that will not accept a PDF, or produce a thumbnail.
Around 150 DPI is comfortable for viewing on screen, and 300 DPI is the usual choice for printing or for feeding into OCR. Higher values mainly produce larger files without visible benefit on screen. Note that 500 is the ceiling this server accepts - the input will let you type 600, but the conversion is refused above 500 because of the memory a render that size would take.
PNG for pages of text, diagrams or line art - it is lossless, so edges stay crisp. JPG for pages that are mostly photographs, where it produces a much smaller file.
The conversion produces one image per page. To combine them into a single tall image you would need an image editor afterwards.
The DPI is too low for the size you are viewing at. Re-run at 300 DPI - text is rendered at the resolution you request and cannot be sharpened afterwards.
Files are uploaded over an encrypted connection and processed on CoonTool's own server, not in your browser. The working copy is deleted automatically once the job is done, and in any case within 24 hours. Nothing is stored permanently and no account is required.