QUESTION - Is there a way for someone to post a PDF to a URL online and make it appear that it was posted to a particular forum even though it never was?

Hypothetically, if a bad guy has a phony letter about, say, President Trump (a completely bogus letter that the person created to make President Trump look bad) could they post it to a website but then DISGUISE the URL by making it look like the document came from a legitimate site when, in fact, it's really something that the bad guy created and posted?

Just trying to figure out the origins of something I found that I know is phony, but I'm not sure how it could have made it up online on what appears to be a legitimate site.

Additional fact – a search of the additional site does NOT result in the phony document. Meaning, the phony document cannot be found there, so that's why we're thinking there's a proxy or something involved.

Thank you for any feedback and ideas you may have.