A method, an apparatus and a computer program enable viewing of data of documents to be printed on a client computer. A client computer includes a version y of a conversion function for converting document data into raster image data and a version z of a client viewer application. A print server includes a version x of the conversion function and a version x of the client viewer application. The method includes the steps of replacing the version y of the conversion function by the version x of the conversion function on the client computer, if the version x is more recent than the version y; installing the version x of the client viewer application on the client computer, if the version z is different from the version x; converting the document data on the client computer; and displaying the image data.