Calculate File size in the Runtime

Hi geeks,

         My requirenments is i have to convert the smartform into PDF and send a mail to the customer.I have done this part using function module SO_NEW_DOCUMENT_ATT_SEND_API1.

         But before sending a mail,i need to calclate the PDF or EXcel file size in the runtime ,IF File size limit is exceeds for the customer then i need to move the Files in to application server.

       1)  Can anyone know how to calculate the file size in the run time ?

        2)  If i move the PDF internal table into Application server as it is,can we download as PDF from Application to Presentation server ?will it works?

       If anyone know the solution i will b gratefull to them...its really very urgent.

Thanks in Advance,

Srini