Chrome - Can't download pdf files

I've just realised that I can no longer download or save PDF files opened up in Chrome while browsing.

PDFs will download when using my Windows 10 laptop in Chrome, and will also work when using Firefox on the Mac.

PDFs open up fine, I can use the other tools such as print, rotate, zoom in/out all work fine, I just can't save them via the "disk" icon in the top right hand corner. I have also tried right click save-as but it only allows me to save as a HTML file.

Any ideas?

Specs: Yosemite 10.10.5, Chrome 48.0.2564.116 (64-bit), Adobe Reader 2015.010.20056