Pocket provides a place to archive and tag or organise content. What format that content is in ... I could care less.

For PDFs, my main problem is in organising metadata. Especially on a tablet, where despite having ample storage, the only real organisation schemes I can come up with are expressive filenames (which are a pain to apply) and directory-based storage.

For both, my best way of accomplishing this is through a Linux environment such as Termux, and an external keyboard.

Tools such as Calibre or Zotero would be handy. Niether has a full-featured tablet port.