If, when you click on the PDF link, it does not download, there may be an incompatibility between your PC and the resource. Please try right-clicking and saving the PDF from the link, instead of opening the full text. When you then open the PDF from the saved version it should work properly.
If the problem is occurring with Elsevier, they are aware of some problems that people are experiencing downloading PDFs and have produced a help-sheet aimed at specific browser users so it might be worth having a look at if you are in Elsevier.
Need help now? Ask your Librarian