To attach files to topics, click the ‘upload’ button when in the editor window (highlighted in red in this screenshot):
Choose your file in the dialogue that opens:
and save the topic.
You can also edit old topics to add files.
If you add a file rather than an image, it will appear as a download link like this: test.pdf (16.5 KB)
At the moment we have only enabled the upload of pdf documents to reduce security risks, but if you find you need to upload different file types, let us know and we will try to make it happen.