In early 2013 LinkedIn make a major format change in an attempt to become a more visual platform as other social media sites such as Facebook, Pinterest, Instagram, etc. Prior to then we had to use complex tools (other 3rd party applications such as Box.net). I covered the details on how to add Rich Media Files to your Summary, Experience and Education sections of your LinkedIn profile in my blog article on January 7, 2013. This procedure now applies to large files, over 100 mg. I would suggest you read Easy Steps To Add Rich Media To Your New LinkedIn Profile for instructions on adding those larger audio, video and presentation (i.e. PowerPoint) files to your profile.
Now you can upload smaller files directly from your computer. These include presentations, PDFs as well as images. Just look for the icon pictured above that looks like a monitor with a ‘plus’ sign on each one of your Experiences as well as Education sections, as well as (there is, of course, only one) Summary section.
These are the formats supported as of 9/17/13:
Note: 100 mg is a rather large file.