Actually he's right. I tried opening it in the browser and downloading it and it is empty. Since it was only recently published I would wait until sometime next week and check again. Mpilchfamily is right though, if you aren't PRO you can't download or view pdfs.
What PDF are you talking about? Did you click the download PDF on the instructable? If so you won't be able to view it cause your not a premium member.
PDF Downloads As a Pro member, you will gain access to download any Instructable in the PDF format.
You also have the ability to customize your PDF download.
Due to http://www.repairpdf.pdfrepairtoolbox.com saving in any revision of the PDF format