Error in attached pdf document

Hi Gurus

I'm sending mail with PDF attachment using FM SO_NEW_DOCUMENT_ATT_SEND_API1. My problem is sometimes it works but othertimes the attachment does not open and message comes "There was an error opening this document.The file is damaged and could not be repaired "

I have tried all the options but still the problem is coming ................

Any idea?????????

Regards

Swatantra

Swatantra