Are their any configurations in IBR, where PDF optimizations can be specfied?Actually, this is not a question directly about IBR. If you see this link: http://docs.oracle.com/cd/E23943_01/doc.1111/e10800/c03_pdfi_all.htm#sthref255 IBR is just a server, which processes conversions, but conversions themselves are performed by other technologies. Oracle now holds two of them: OutsideIn, and OpenOffice, but you can also use Microsoft Office or other 3rd party conversion tools.
Can this low resolution PDF file be created after the workflow is approved?It certainly can. I am not, however, aware of any method how to do this with a customization.
I expect Web optimized PDF to be lesser in size and will be easily consumable if sent to some web address.I don't see any reason why it should not be. In fact, even textual PDFs can be optimized - for instance, from our case I know that an approximate PDF/A is about twice that large than the original PDF (PDF/A is a format required for long-term content preservation, and it also contains e.g. true-type fonts so that the content can be rendered properly even on workstations without them). Another good example can be transformation of graphical PDF (scanned text) to a textual one - this is, however, more a task for OCRs than converters (WebCenter Capture from Oracle portfolio).
Do you think if this is possible??