When the PDF displays, click the disk icon in the viewer's menu bar:

(If your Adobe toolbar's missing this icon, just control-click or right-click somewhere on the toolbar, scroll down to "More Tools...", and add it.)
Control-click (Mac) or right-click (PC) on the PDF and select "Save Frame As...".

Instead of (or in addition to) saving PDFs to your hard drive, you can mark them as "keepers" so you can access them from any online computer. Just click in the check-box in the upper right-hand corner of a result:

The result will be kept until you uncheck the box. Your keepers are your own; the only person who can access them is you (by logging in). You can see all your keepers by clicking on "keepers" at the top of the results list:
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