I described already earlier how to use images in pdf format in your LaTeX document, e.g. if you want to include a screenshot of a Table of a paper in pdf format in your slides (which results in much better quality than using jpg or similar formats).
But what if you want to include complete pages of a document or even complete pdf documents? I have used the latter for example as a reliable tool to append pdf documents, such as papers.
You just need two commands
\usepackage[final]{pdfpages}
in the preamble and
\includepdf[pages=-]{YOUR_PDF_DOC.pdf}
If you set “pages=-“, the whole pdf will be included. If you just want to have selected pages, enter them instead of the dash.