The URL’s from most other publishers can be copied from the browser address bar.
For example, Highwire Press, Wiley-Blackwell, New England Journal of Medicine, JAMA, Annals of Internal Medicine all display direct links to the PDF in the address bar. But, you actually have to click on the link and go to the full text in order to copy it.
A slightly quicker way is to RIGHT Click on the full text/PDF link; go to Properties; then copy-paste the link into the Unique Identifier box on the Word Document.
*TIP: Also, publishers frequently have a notation on How to Cite this Chapter, e.g., this chapter from Harrison’s, which includes the persistent URL:
Dunaif Andrea E, "Chapter 6. Women's Health" (Chapter). Fauci AS, Braunwald E, Kasper DL, Hauser SL, Longo DL, Jameson JL, Loscalzo J: Harrison's Principles of Internal Medicine, 17e: http://www.accessmedicine.com/content.aspx?aID=2860060
Otherwise, the URL displayed in the address box is persistent.