A small project add PDF documents as a custom content to SharePoint 2010. Requires Adobe Reader on the client.
Project includes:
1) PDF Custom Content Type sandbox solution for SharePoint 2010.
2) A SharePoint IE OpenDocuments class for opening PDF files using Adobe Reader.
3) A installer and Com register program for the OpenDocuments Com server that does not require client administrator rights. It registers the OpenDocuments Com+ server in the current user registry hive. Published as a click once program.

Steps:
1) Only farm administration action to add the Sam.Craven.OpenDocuments to the docicon.xml file in the SharePoint 14 bin template\features folder:
<Mapping Key="pdf" Value="icpdf.png" EditText="Adobe Acrobat" OpenControl="Sam.Craven.OpenDocuments" />
Line should already exist if the PDF iFilter was installed.

2) Deploy the PDF content type sandbox solution to the target site collection (site collection administration rights required).

3) Publish the click once application for installing and registering the OpenDocuments Com+ server.

5) Have each user install the click once application and register the OpenDocuments Com+ server.

6) Enable the OpenDocuments Com+ server in IE.