Search does not appear to working with the latest version of the front-end. I downloaded the latest code from GitHub. Here is a forum post requesting this specific feature. Usually their support team is good about updating forum posts when updates are released.
mso-bidi-language:AR-SA”>I get the feeling that search only works with HTML
format even though their blog post indicates all front-end features from
version 2.x have been implemented. Can you post a question on the forum
specifically asking if search works with Image formats using GroupDocs Viewer
for .NET 3.3.