Windows: Microsoft Edge
Right-click the PDF, choose Open with → Microsoft Edge, then select Read aloud in the toolbar or press CtrlShiftU. Edge highlights each word, and you can change the voice and speed. Its natural voices are the ones marked Online and need the internet; offline it falls back to Windows' standard voices. More on Edge's Read Aloud.
Windows or Mac: Adobe Acrobat Reader
Choose View → Read Out Loud → Activate Read Out Loud (ShiftCtrlY, or ShiftCmdY on a Mac), then Read This Page Only (ShiftCtrlV) or Read To End of Document (ShiftCtrlB). It uses your computer's voices and works offline. You have to activate it again for each PDF you open.
Mac: Preview
Open the PDF in Preview and choose Edit → Speech → Start Speaking. Select a passage first to hear just that. For better voices, download a Premium voice in System Settings → Accessibility → Spoken Content.
Chrome
Chrome has no read-aloud button for PDFs of its own. Extensions such as Read Aloud work in Chrome's PDF viewer; for PDFs on your computer, turn on Allow access to file URLs in the extension's settings.