You can search content, provided the content in the document is searchable (i.e. a Word document is searchable, but a JPG file is not). You can also search against tags.
From the Documents dashboard, click the blue Advanced Search button:
Here you’ll be given additional search options, as shown below:
You can search text/content, tags, last modified, and last modified by. Be sure to check the Search within documents box to enable this feature (otherwise, the system will restrict the search to document name). Click Search to conduct your advanced search.