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.
http://www.groupdocs.com/Community/forums/12228/viewer-3.0-search-not-working/showthread.aspx#12228
<span style=“font-size:10.5pt;font-family:“Arial”,sans-serif;mso-fareast-font-family:
Calibri;mso-fareast-theme-font:minor-latin;position:relative;top:-1.5pt;
mso-text-raise:1.5pt;mso-ansi-language:EN-US;mso-fareast-language:EN-US;
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.