You can attach files within IM. By clicking on the file attachment icon in the message field: 
The settings for the uploads and file extensions can be found in BuddyBoss/Settings/Media/Documents. We only use the size from Documents for all file types. Your server will have a maximum upload size that appears below the Upload size that you can enter. At this time, with im for BuddyBoss, we only allow 1 upload per message, the Upload limit does not do anything.
The File Extensions is where you can choose what file extensions you will allow to be uploaded. Once upload, images, gifs and videos will open in model when chosen. Application files like Word, Excel and PDF will be downloadable for viewing. Images and videos will also open in the modal window. They too can be download, The modal includes a X to close the window
Application file Example (Example, highlighed, is the file name):
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