Hi Stuart/Sturico,
Thanks for using Syncfusion Products.
The PDF files generated by Essential PDF can be viewed using Adobe Acrobat Reader 7.x or later versions. Other conforming readers that strictly follow Adobe's PDF specification 1.4 or later also can be used. Please go through the following link.
http://help.syncfusion.com/ug_84/Reporting/PDF/ASP.NET/default.htm?turl=Documents%2Fpdfversioncompatibility.htmRegards,
Selvakumar.