Skim is a PDF reader and note-taker for OS X. It is designed to help you read and annotate scientific papers in PDF, but is also great for viewing any PDF file. Skim requires OS X 10.10 or higher.
iTeXMac is an integrated software which components are:
- a text editor dedicated to D.E. Knuth's TeX typesetting system
- a frontend to a teTeX like distribution, that includes TeX engines and tools
- a PDF viewer