Is your suggestion for improvement related to a problem? Please describe.

Currently, Document Viewer (which can be opened through Main Menu -> View -> Open Document Viewer) shows all linked files, but it only can display PDF files.

Describe the solution you'd like

Filter out only PDF files in the combo box of Document Viewer, to show only PDFs.

Additional context

Well, Document Viewer is named Document Viewer, but it can't display .docx or .tex (it certainly shouldn't display .tex, but it's other topic).