Pdf file compress

Dear Sir,

here one pdf file containing mark sheet of a student. the file size is 757 kb. the document is to be upload on a software which is showing message that the file size must be less than 50 kb size in pdf. I tried number of softwares to compress the size. but till i am unable to compress the size upto 50 kb. please suggest the solution as early...

Narhare Maruti.