This members-only tutorial provides the steps to display icons that represent the type of files when outputting the values of File-type of custom field that is inside a ACF Pro's Repeater.
Step 1
Install and activate ACF Pro.
Custom Fields → Field Groups → Add New.
Title: Page Fields (in this example, we are going to attach the field group to page post type, change this accordingly if needed)
Add a Repeater-type of field called "Files" (so the Field Name is files).
Add a File-type of sub field called "File" (so the Field Name is file) inside the Repeater.
Leave the Return Value as the default, File Array.
In the Location meta box, select where this field group should be available on.
Step 2
Edit your Page(s) and populate the field group.
Step 3
In the Page/Template that applies to your post type, add this PHP: