Namely, is it possible to add a button inside the page layout, which will have the same functionality as described here: http://help.adobe.com/en_US/digitalpubsuite/using/WSf6ef983f54a76485-3 d39e50113568f15d7f-8000.html
By social sharing links, you mean you want to embed a hyperlink as a button on your document?
With DPS, you can enable social sharing features. When its enabled, your end users reading through articles on thier tablets can share the articles on thier facebook walls, twitter, copy the article link and send it through e-mail, or even copy the article link and post it somewhere on the web.
For detailed info on how to enable social sharing with your DPS apps, go here http://helpx.adobe.com/digital-publishing-suite/kb/setting-dps-app-soc ial-networking.html
setting a button on your document with a hyperlink will not have the same features as discribed in the article above. Yes, you can add a button and make it a hyperlink to a social sharing site. But that's all about it. But with DPS social sharing integration, it work differently. Check my other reply to @Steve