Placeholders enable you to insert values from the data. For example, they can be used to display the name of the customer, the booking price or similar data in the document. The value is defined in the field "Property". You can find a documentation for the expression syntax by clicking on the question mark besides the input field.
Additionally, you can enter a preview for the placeholder. If you enter a value, it will be displayed in the editor. By providing proper previews, the layout of the document is not distorted by overly complex expressions.
Needless to say, custom fields can be display in docuents as well.They are available under the specified PDF Placeholder Name in the custom field configuration.
If fou example the number of seats should be printed in a document, the first thing to do would be to check for the PDF Placeholder Name of the custom field.
So in this case it's "seats". because it is a property of an object, it can be found under the object key. So the final placeholder would look like
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