Right click on your project and click on **Edit**:  This opens the **Project Settings** page. Click on **Attachments** in the left hand panel:  Then click on **Click to upload** in the window that opens: 

So you can associate a file, but you can't view that file anywhere in EasyEDA. You will have to download it again, and edit it locally on your own PC. I was thinking of some way of adding text or markdown files which can then be opened and edited in a tab in the main EasyEDA window, along with PCB's and Schematics. willem

@nlitsme, A couple of options. In a couple of projects, I have used a blank Schematic as a text sheet just by adding text fields but there's no way to upload a text file and then open it from within a schematic sheet. You have to be careful though because there are some characters and strings (such as `