Before uploading any of your articles to an academic networking or institutinal/disciplinary repository, be sure to check out the Sherpa-Romeo database http://www.sherpa.ac.uk/romeo/ which provides information on publisher copyright including self-archiving and uploads to disciplinary or institutional repositories or sites like RG (usually in pre-or post-print format, not publisher PDF) for specific journals. Of course, the actual contract signed with any author addendum that specifically reserves copyright and/or archiving rights to the author(s) would be the final determinant for individual cases. Other special cases include grants-funded articles which require open access immediately or within a specified period.
More copyright resources to be added here soon!
Descriptions coming ;-)