ADOBE ACROBAT READER DC
It is obviously the main software for viewing pdf files although it does not have functions to modify the text, such as highlighting some sentences or notes next to the text. It can also be a bit heavy for some PCs.
The premium version allows editing of files
As popularity is the most popular software that makes it among the most viable alternatives to acrobat reader.
Compared to acrobat reader, it has some more functions: highlighting and writing notes. In recent years it has become a bit heavy.
Sumatra PDF is a slim, free, open-source PDF/DjVu/EPUB/XPS/CHM/CBR/CBZ/MOBI viewer for Windows. Sumatra has a minimalistic design. Simplicity has a higher priority than a lot of features. Its small and starts up very fast.
Its designed for portable use: its just one file with no external dependencies so you can easily run it from external USB drive.
PDF-XChange Viewer is an alternative viewer for PDF files that enables you to view and annotate PDF files.
It is a very light software but has a very spartan graphic.