Per the display tag library documentation you should be able to specify any properties that you need in the displaytag.properties file OR within the display:table tags in you code.  I have usually opted for that latter as the properties are specific to the table I am programming rather than across the board functionality within your application.

At least one of the properties can not be used this way.  It must be specified in the properties file.  The export class to use, as in:

export.pdf.class=com.myweb.PdfView

It is the only way to get displaytag to invoke your code.  If you run across other properties that are not being picked up, try moving them to the properties file.  Bet it will work that way.