PDF Export displays blocks in the file name for Attachments named using Chinese Language

Summary :

 When a ppt file is saved with file name in Chinese and attached to the page, while exporting the Confluence page as pdf, the file name in the PDF export shows  garbled Chinese characters in blocks.

 Steps to reproduce

1. Create a page and attach the ppt file with file name in Chinese (used Ukai font for testing)
2. Make sure Ukai font is selected from Confluence Administration (Cog Icon)  > General Configuration > PDF Export Language Support
3. Export the page as pdf
4. File itself is displayed fine in display and edit mode
5. File name in the pdf export shows the Chinese characters in square blocks.

Expected Results

1. The file name in the PDF export should show the Chinese characters.

Actual Results

PDF export shows square characters for the file using Chinese characters as file name (Screen shot attached).