Emacs support library for PDF files
PDF Tools is, among other things, a replacement of Emacs's DocView for PDF files. The key difference is that pages are not pre-rendered by e.g. ghostscript and stored in the file-system, but rather created on-demand and stored in memory. This rendering is performed by a special library named, for whatever reason, poppler, running inside a server program. This program is called epdfinfo and its job is to successively read requests from Emacs and produce the proper results, i.e. the PNG image of a PDF page. Actually, displaying PDF files is just one part of PDF Tools. Since poppler can provide us with all kinds of information about a document and is also able to modify it, there is a lot more we can do with it.
pkg install pdf-tools-emacs_wayland