Available from version 1.13+
Use metadata to store custom information for tagging and labeling back to your internal systems. Lob metadata structure can hold 20 key- value pairs, each metadata key must be less than 40 characters long and values must be less than 500 characters.
PM supports the ability to configure the Salesforce field/data to be mapped to Lob metadata key/value for Letters, Postcards, and Checks as part of the Print & Mail object. Print & Mail. There is a field, Metadata__c, available on Print & Mail object. Data can be added in JSON format which gets transferred to Lob when PM record is processed.
PM app retrieves all Metadata values from Lob for Letter, Postcards, and Checks via webhooks. PM app stores the Lob metadata in a long text area fields named
cp_print__Metadata__con the Print & Mail object. The Metadata is stored in JSON format and can easily be converted to a key-value map in Apex code to retrieve a value by key. The field, Metadata__c, is available on Letter, Postcard, and Check layouts.