Ok, I see this in the 3.6 release notes. I think this helps me up to some extent . But still its good to have this working when exporting manually or in dashboard .
Full PDF and CSV Generation
You can now generate PDF files and CSV files containing the full set of data. Previously, only the first page of a dashboard was attached and sent in an email message. If you select all pages, an email message is sent with a time-sensitive link to the report containing all pages. For more information, see Share Data with Other Users.