If you're looking for a quick way to edit or sign a PDF document, there are free and easy-to-use tools for iOS, Windows, and Android devices.

I’m going to guess that your older computer–the one that previewed .pdfs–ran the 32-bit version of Windows 7, and that your new one, with its more powerful processor, uses the 64-bit version.

You can save a webpage as a PDF on a Windows computer using any installed web browser's Print menu and selecting "Save as PDF" from a dropdown menu.