If you have Chrome showing you the PDF rather than Adobe, you can not use this 'preview by chrome' to save the PDF to NetDocuments. You must open the PDF in Adobe reader instead.
To disable PDF viewer in Chrome
(look halfway down the page for " Turning off Chrome’s Built-in PDF Viewer and using Adobe Reader or Acrobat instead"
This is assuming that you have Adobe Reader installed.
Once this is done then when you view a PDF on the web it will open in Adobe Reader and then you will be able use SAVE AS function to save the pdf to Netdocuments. (be sure to click 'choose another folder' button on the save as screen to bring up the ND Screen.