estimatedSize

The estimated size is part of the size that will be reserved in the PDF document before digitally signing it. This size corresponds only to the /Contents field of the signature field, that is, the signature container. Core will actually reserve a bigger space to make room for implementation details (the /ByteRange field, the fact that a signature is hex-encoded in a PDF, etc.). A big estimated size will possibly make the signed document bigger than necessary, but a too small one will cause the signing process to fail. The value will be clamped to the nearest even value between 0 and 256 KB (262144 bytes). If not set, the default is 32 KB (32768 bytes).