Perhaps a single system is not the answer, but a combination, e.g. for taking notes I'd pick fedwiki/sublimeless_zk/Zim/org-mode.
For organizing PDFs with full-text search Zotero is quite good, and you can link to your PDFs from your notes, but I wouldn't store my notes about PDFs inside Zotero (because then it'd be separated from my notes about non-PDF articles).
For keeping track of articles Firefox bookmarks (with Firefox Sync on Android acting as a 'read me later' bag).