Many of the PDFs you download from Library databases have a form of the CrossMark logo on the title page of the article. This logo provides you a way to check if the article has been corrected or retracted (this information would otherwise be time-consuming to obtain). As long as you are connected to the internet, you can click on the logo within the PDF and you will automatically connect to a website letting you know whether there have been any corrections.
For a (humorous) look at how this works, try selecting the CrossMark logo on this PDF.
I love psychoceramics!