1. "While running a case, I have attached one pdf document. I want to know where that document is stored in pega"
Document is stored in PC_DATA_WORKATTACH table. Mapping b/w an attachment and a case is stored in PC_LINK_ATTACHMENT.
2. "Then I want to show that downloaded pdf in a section in the tabbled layout."
There're several ways. It depends on what you want to show in your repeating grid. The starting point is the data page D_AttachmentList with pzInsKey of your case as parameter. D_AttachmentContent will give you insights about each particular attachment
Thanks for your response. Can you please explain how to add that pdf in a section.I have dragged one section and I have given the data page as source "D_AttachmentContent". It is asking for the section. What section name I have to give in order to show that pdf(ie. Which I have attached while running the case)