The upload attachment feature will now only allow PDFs to be uploaded. Since these files are opened with the internet browser, there is no way to determine how each different browser will render each type of file and can produce unexpected results.
Most files can be saved as PDF simply by choosing "Save As" and selecting PDF from the file type box. You can also install a PDF printer and "Print To" a PDF.
The functionality to add a URL as an attachment has remained unchanged.