As suggested by the Happiness/Support Engineer, I am giving below the old and new file names. Both the names are in Unicode (Script = Devnagari Marathi, Language = Marathi, an Indian language spoken by about 110 million people).
1. OLD FILE NAME = अमृतमंथन_हिंदुस्थानी संगीताची आणि संस्कृतीची लाहोरी शोधकथा_ले० अंजली कीर्तने_101212
2. NEW FILE NAME = अमृतमंथन_लाहोरी शोधकथा_ले० अंजली कीर्तने_101212
Whenever I tried to upload the pdf file with the old name, in the upload dialogue box also it showed file name as just 'pdf'. Thereafter whenever one tried to open the file in the article by clicking on the link in the article, it just downloaded the file without opening it. Later when I noticed the short name 'pdf' in place of the complete name, I suspected that it had to do something with the name. So I tried giving a shorter name, which worked.
You may check out the article at the following link.
I hope this information would enable you to detect the bug and rectify it. If you need any more information, please do let me know.
Thank you very much.