1. Go under Reports to Standard Reports.
2. Find the Expense Report you want to edit and click it's name.
3. Click on "Fields to Display" to expand this section.
4. In the "Fields to display in report" section, find the item labeled "Expense Attachments" and click Add. See the screenshot below for where this option is.
5. Save and Run the report.
If there are attachments to view there will be a pair of buttons at the bottom of the report: Show Attachments and Print PDFs. Show Attachments will load all of the Attachments on the same page that you can print. PDFs are strange in that, since they can be multiple pages, only their first page will be shown like this. If you have PDFs use Print PDFs to get those files.