1. A computer-implemented method of mapping content from a structured starting template to a pre-generated structured target template comprising: providing, by a computer, the structured starting template in an application for a document and the pre-generated structured target template in the application for the document, wherein the starting template and the pre-generated target template are configured for the same display media, the starting template and the pre-generated target template transform a document layout of the document of the application to another document layout for the document of the application by: analyzing, by a computer, the starting template to determine when content objects are associated with the starting template; determining, by a computer, object properties associated with the content objects that are associated with the starting template; determining, by a computer, physical relationships between the content objects that are associated with the starting template, the physical relationships are represented by a proximity graph having the physical relationships of the content objects that are associated with the starting template; determining, by a computer, contextual relationships between the content objects that are associated with the starting template, the contextual relationships between the content objects that are associated with the starting template are represented by a relationship tree; analyzing, by a computer, the pre-generated target template to determine when content placeholders are associated with the pre-generated target template; determining, by a computer, object properties associated with the content placeholders that are associated with the pre-generated target template; determining, by a computer, physical relationships between the content placeholders that are associated with the pre-generated target template, the physical relationships are represented by a proximity graph having the physical relationships of the content objects that are associated with the pre-generated target template; determining, by a computer, contextual relationships between the content placeholders that are associated with the pre-generated target template, the contextual relationships between the content objects that are associated with the pre-generated target template are represented by a relationship tree; generating, by a computer, potential content mappings from the starting template to the pre-generated target template for mapping the content objects that are associated with the starting template to the content placeholders that are associated with the pre-generated target template based on the object properties, the proximity graphs of the starting template and the pre-generated target template, and the relationship trees of the starting template and the pre-generated target template; rating, by a computer, the potential content mappings according to rating factors, the rating factors are based on maintaining the object properties associated with the content placeholders to the object properties associated with the content objects, the physical relationships associated with the content placeholders to the physical relationships associated with the content objects, and the contextual relationships associated with the content placeholders to the contextual relationships associated with the content objects; determining, by a computer, which content mapping is an optimal content mapping for mapping the content objects associated with the starting template to the content placeholders associated with the pre-generated target template, the optimal content mapping being the highest rated content mapping according to the rating factors; selecting, by a computer, the optimal content mapping; mapping, by a computer, the content objects that are associated with the starting template to the content placeholders that are associated with the pre-generated target template according to the optimal content mapping selected from the content mappings; and displaying, by a computer, the pre-generated target template after mapping the content objects that are associated with the starting template to the content placeholders that are associated with the pre-generated target template according to the optimal content mapping selected from the content mappings.