9. A system for generating a variable-data printing document template, the system comprising: a processor which is adapted to: receive from a user a variable-data printing document template definition, the template definition comprising a layout of document pages with at least one set of the document pages including a flow that contains content which is variable in response to the input data, the flow spanning across the at least one set of document pages; receive from a user a plurality of document versions, wherein at least some of the different document versions comprise a different series of the respective document pages of the at least one set of document pages, and indicate the desired variable content of the flow, wherein the template definition is configured to automatically maintain the continuity of the flow when any one of the respective document versions is automatically selected in response to input selection data during variable data merging, wherein automatically maintaining the continuity of the flow, when the automatic selection of a respective one of the document versions results in an absence of a document page of the at least one set of document pages across which the flow spans, is performed via a conditional choose function such that: in the event that all pages of the at least one set exists in the input data, applying a first page sequence definition that maps the flow to span across all pages of the at least one set; and in the event that an intermediate page of the at least one set is non-existent in the input data, applying a second page sequence definition that remaps the flow to begin with a first page, include all pages of the at least one set prior to the intermediate page, and include all pages of the at least one set subsequent to the intermediate page.
9. A system for generating a variable-data printing document template, the system comprising: a processor which is adapted to: receive from a user a variable-data printing document template definition, the template definition comprising a layout of document pages with at least one set of the document pages including a flow that contains content which is variable in response to the input data, the flow spanning across the at least one set of document pages; receive from a user a plurality of document versions, wherein at least some of the different document versions comprise a different series of the respective document pages of the at least one set of document pages, and indicate the desired variable content of the flow, wherein the template definition is configured to automatically maintain the continuity of the flow when any one of the respective document versions is automatically selected in response to input selection data during variable data merging, wherein automatically maintaining the continuity of the flow, when the automatic selection of a respective one of the document versions results in an absence of a document page of the at least one set of document pages across which the flow spans, is performed via a conditional choose function such that: in the event that all pages of the at least one set exists in the input data, applying a first page sequence definition that maps the flow to span across all pages of the at least one set; and in the event that an intermediate page of the at least one set is non-existent in the input data, applying a second page sequence definition that remaps the flow to begin with a first page, include all pages of the at least one set prior to the intermediate page, and include all pages of the at least one set subsequent to the intermediate page. 10. The system of claim 9 , further comprising a printer, which is adapted to receive input selection data which defines a respective one of the document versions, and generate the respective defined document version from the input selection data and the document template.