Can you be a little more specific? Are the white lines around the edges or are they within the photo itself? I'm not sure what white lines you might be referring to unless I can see an example of such an image. Would that be possible?

If around the edges you can crop the edges using Photoshop. For printing purposes on white paper I'm not sure the edging white lines would make a big difference, but it might.
There's generally more than one method of dealing with things with Photoshop.
For example, you could potentially duplicate the bottom layer, either mask the layer or select the white lines and either delete or stamp over. Then move the other image segments one by one together by a pixel or two.