The inside attachment search procedure is thus: For instance, you need to locate a statement within your document, lets say "Search Innovations", simply input "has:attachment Search Innovations". And for format specified search, input: "has:attachment format: search term".
The feature, however may not be a novelty as other email systems already incorporate the attachment search capability. Albeit, Google for reasons best known to it had delayed the implementation on its webmail service.
The roll-out of the feature has commenced, but certainly has not been extended to all Gmail users. The good news still remains that Gmail now fully support searching inside attachments.