Q: How do I save a downloaded PDF on my phone or tablet?

I clicked a link to a PDF from within an app (such as MIT Atlas) on my phone or tablet, and I wish to retain a copy of this file. How do I do that?

For Apple iOS devices

Open the desired document. In the case of the MIT Atlas app, this would be done by clicking the "Download" button indicated in red here:

Clicking the "Download" button should open the PDF, which can then be saved by clicking the "Share" icon indicated in red here:

For Android devices

Click the "Download" button for the relevant document:

Select the application you wish to view your PDF in. Most Android devices should have at least one of these options and all will work:

If you do not have any applications listed here, you may need to download a dedicated PDF reader app, such as Adobe Acrobat.
Adobe Acrobat Reader can be downloaded here: https://play.google.com/store/apps/details?id=com.adobe.reader&hl=en_US&gl=US