Represents the "CheckSum" entry of the embedded file parameter dictionary object.

It is an optional entry defined as part of the PDF 1.0 specification.

It contains a string representing a PDF string object.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 46, page 104.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 45, page 137.

The CheckSum entry holds a 16-byte MD5 digest of the uncompressed file data. A reader that extracts the file can compute the MD5 digest and compare it with this value to verify that the embedded data is intact.