Greetings,
You can find more information about the current PDF annotation technology used within the EndNote for iPad app on our website here:
The following knowledgebase article includes steps which would allow you to use annotation tools within another iPad app:
Please let me know if this helps.
Best Regards,
Jimmy M.
Customer Technical Support Representative Scientific
Thomson Reuters
Phone: +1 800 336 4474
ResearchSoft Product Support
thomsonreuters.com