Occasionally you might try to download a PDF and (after waiting a super long time) get an error telling you that your PDF is corrupted.
That message generally means that your download timed out. This may be because of a lackluster internet connection or a large download size. Sometimes articles with tons of images will have trouble too.
The easiest way to get your PDF is to cut the problem off at the pass. Right click on the "Download PDF" button and select "Save Target As..." (or in Firefox "Save Link as..."). This will allow you to save the PDF to your computer and should allow for a faster, more successful download.