Are PDF files viewed on the web downloaded anywhere?

It has to be downloaded or else you would not be able to see it.
If you are uising Safari, the cache is ~/Library/Caches/Safari.

stanwelks wrote:
When you open a PDF from a website, is it downloaded anywhere on your Mac in a cache folder or somewhere else? I viewed some bank statements on another Mac and am just curious if it is still saved somewhere on it.

Thanks.

It may be in your browser cache, or, depending on the situation, it may simply use RAM, in which case, while technically a download, it's ephemeral and disappears when that memory is overwritten or when you turn off the computer. Sometimes even RAM is cached, but If you have "Use secure virtual memory" turned on, the cache is encrypted.

~/Library/Cache/Firefox/Profiles/f5xxxx.default/Cache