PDF files can be viewed on any Mac or Linux computer, or on Windows, using the Adobe Reader program available for free here. The page layout of the PDF is exactly the same as the print magazine, and is best read on a large screen.
ePub can be used on multiple platforms including iBooks (macOS / iOS), the Nook, the Sony Reader, Android, etc. If you want to read the ePub format on your Windows computer, you can download the free Adobe Digital Editions software. Barnes & Noble also has free Nook reading apps for Windows and Mac.
The mobi edition can be read on the Kindle e-reader by copying the file into your documents folder on your Kindle. The easiest way to do this is the Send to Kindle app. Alternately, you can transfer the file over USB or e-mail the downloaded issue to your Kindle. To read the mobi format on your computer, download one of the free reading apps from Amazon.