TPdfSigner.EstimateLength Method
Returns the estimated length for the data that will be returned in GetSignature. Note that this method will be called before finishing the pdf, so you still don't know what the final signature will be. You can return a number larger than what GetSignature will return at the end of the pdf creation, but never smaller.
Syntax
Unit: FlexCel.Pdf
function TPdfSigner.EstimateLength: Integer; virtual; abstract;