PDF files are generated based on the Design Considerations for PDF Rendering
and Acrobat 8 must be able to open the files for preview.
To my knowledge, there are no changes in the PDF rendering that may cause the content to be flipped or reversed. also tests with the local examples of the latest Q3 2015 and the mentioned Q2 2015 Telerik Reporting versions do not point to such issue.
Please check if you have enabled TextBox items' RTL support
by changing the current threads culture. In such case the text will be displayed RTL in both viewers and rendered documents.
In order to provide you more accurate suggestions, please open a support ticket and attach a demo project including a report and test data reproducing the problem.
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