Sumatra PDF

Sumatra PDF is a lightweight PDF reader for Windows. Compared to Acrobat Reader and even Foxit Reader, Sumatra is simpler in its UI and faster to open. One of the coolest features is that when you open a PDF that you had opened before, it goes directly to the page and zoom level which you were at when you had closed it! I highly recommend Sumatra PDF as the primary PDF reader on Windows.

• Highlight: To annotate by highlighting, visually mark the text using the mouse and press a.

If you press A instead, the text is highlighted and also the Annotation Editor side window pops up showing all the annotations and options to configure or edit the annotations.

To change the default highlighting color, go to Settings -> Advanced Options and search for HighlightColor.

• Underline: Select the text with the mouse and press u. Underlining can be done on top of already highlighted text - this is something I could not do even in Adobe Acrobat Reader!

To change the default underline color, go to Settings -> Advanced Options and search for UnderlineColor.

• Add text: To add text directly on the PDF, right-click and choose Create Annotation Under Cursor -> Free Text. This brings up the Annotations dialog, where the text, font, border and colors can be set.

• Dark mode: Press i to toggle between dark mode and light mode.

Reference

• Full list of keyboard shortcuts

Tried with: Sumatra PDF 3.4.6 64-bit