In Pega 8x, there are two controls that let you attach multiple files to a case.
In this post, I've included a code snippet for both controls that enable to show a progress bar when files are being uploaded as below. Please see attached for How-To document.
*1. Since both of out-of-the-box controls are "Final", you will have to create new controls from scratch. Also you will have to do Save As a series of sections that reference the out-of-the-box controls accordingly.
*2. We've created this because some customers requested it, but it is not really recommended to customize such low level functionality. I would suggest to use the out-of-the-box ones as much as possible, because of two reasons - (1) If any issues occur, it may get hard to know if it is coming from customization or product. (2) When upgrade, product enhancement made to the controls will not be applied and you will miss the chance.
***Edited by Moderator: Pooja Gadige to add Developer Knowledge Share tag***