When the content that is being exported to PDF contains Material Design Icon the exported PDF is not valid.
Currently, when the file is about to be opened with Adobe Reader the following error appears - 'An error exists on the page. Acrobat may not display the page correctly. Please contact the person who created the PDF document to correct the problem.'.
Also if the file is tested in an online pdf validator it is not considered valid.
The exported file should be opened in Adobe Reader without any issues.