Here at Paper.li we don't select the content that is featured in papers.
Paper.li is a service that enables people to create their own topic based newspapers via shared social content. We don't manually place any content on the papers directly or exchange back links. All articles, video or images have been selected by the publishers themselves-- either manually or by them adding keyword searches or thought leaders as a source.
Suggestions for getting your content included
If there is a specific paper that you would like to be a part of, you can try contacting the publisher directly. The publisher is mentioned in the upper right hand corner of the paper ("From the Editor").
Post the content the content you would like to have included on social media sites such as G+, Twitter, or Facebook with the hashtags that represent the audience you are interested in. That will help you get your content featured and discovered.