When you create a new post, you have the option of adding unlimited attachments from your photo library, device or cloud storage, and more.
On mobile, you can find the attachments option in the overflow menu (...) in the bottom right-hand corner.
On the web app, you can attach files by clicking the paperclip at the bottom of the comment box. You can navigate to a folder on your computer, drag and drop or connect to a variety of document storage services.
You can upload any type of files, Photos, videos, PDFs, spreadsheets, Word documents, etc.