According to the documentation, the internal search includes attachments. However, it seems like this only applies to file names. Is it possible to search inside pdf and pptx files themselves?
No, there is no file content search with the built-in search.
Thanks. Has this feature been just not been implemented or are there good reasons against it? I could not find a corresponding feature request on github.
Content search is not something that can be easily done without extra dependencies (that are often rather heavy, need Java, etc.). We usually assume people who need something like this use an external search provider instead.