Local Rule 25.1 on Case Management and Electronic Case Filing for the Court of Appeals for the Second Circuit states in subsection 3 that, "A PDF must be text-searchable. A PDF need not include a manual signature.".
The Second Circuit is not kidding either. If you fail to make all of your exhibits to a declaration text searchable, expect to receive a Notice of Defective Filing the next morning, with this instruction:
"Please cure the defect(s) and resubmit the document, with the required copies if necessary, no later than [THE SAME DAY OF THE FILING!]. The resubmitted documents, if compliant with FRAP and the Local Rules, will be deemed timely filed. Failure to cure the defect(s) by the date set forth above will result in the document being stricken. An appellant's failure to cure a defective filing may result in the dismissal of the appeal." See the example posted here.
See the Tip of the Night for May 18, 2015, for an automated way to find which PDFs in a large set are not text searchable.