Archiving a document simply hides it from view unless the "Show Archived" option is toggled. This is different to deleting a document which permanently removes the file from Simul.
To remove a document from view, select the menu icon on the document tile:
Select 'Archive Document' from the list of options:
The document will now be slightly faded and you will see an option to 'Unarchive document'.
Next time you visit the documents page, this document will be hidden. To show archived documents, use the toggle near the top right of the screen: