How to rename a PDF in library because too long of a filename to recognize as a PDF file.

I have set the auto rename function of Mendeley desktop as Author-Year-Title. Unfortunately, a very long title PDF is just cannot be recognized correctly and opened on my iPad, though it can be opened by Mendeley desktop in spite of the filename type which is named “--_third-o”. How can I solve this kind of problem? thanks! The full filename is as follow, "Spanos, Giaralis - 2013 - Third-order statistical linearization-based approach to derive equivalent linear properties of bilinear.--_third-o", which should be ""Third-order statistical linearization-based approach to derive equivalent linear properties of bilinear hysteretic systems for seismic response spectrum analysis.PDF" in a proper way.