If you generate a multi-article PDF from Portal > Content Tools > Import & Export > Export to PDF, all links among the articles within the PDF do not work. For example, if articles A and B are included in the PDF, and there is a link from article A to article B, that link from article A will not work in the PDF.
This results in a bad user experience, and makes it seem like the PDF is totally broken and we don't know how to do our job as technical communicators.
The problem seems to be that your PDF rendering process does not recognize inline links to other articles as belonging to the PDF itself. Instead, you are coding the link as a relative URL to a website. (See attached screenshot.)
User expectations: If two articles are in the same PDF, and those articles link to each other, the links should work in the PDF itself too. Alternatively, do NOT render inter-article links to look like links. (That said, it would be best to render them as links AND make the links work.)