In RefWorks, you can upload the full-text PDFs of the articles themselves as well - everything is in the same place.
Once you are logged into your RefWorks account, and the citation information has been either electronically or manually entered into your documents, click on the article itself. Doing this will bring up the full information on the right side of the screen.
Next, make sure that the PDF of the same article is downloaded somewhere on your computer - your desktop, your downloads folder - it doesn't matter where, you just need to be able to navigate to it!
Now, minimize the RefWorks screen a bit, so that you can simultaneously see the article information and your PDF at the same time.
Drag the PDF of the article over top of the citation information on the right.
The PDF of the article is now uploaded to your account, and you can read it whenever you want.
Once the PDF is open in RefWorks, you can do more than just read it; you can highlight important parts, and add in comments on the side about things you think are meaningful.