While I can't answer the question specifically as it relates to PageMaker (it's been YEARS since I've used that app!), I can give you some general information that will help.
Generally speaking, 1-bit images (line art, strictly black/white with no grays) are easily made to be transparent. However, they must be saved as TIFFs (at least to use them this way in Quark). In Quark, this involves drawing a picture box, placing the image, and filling the picture box "none" to allow the whites of the image to be transparent.
On the other hand, grayscale and color images will show up with a white background. Quark (and presumably other apps as well) WILL let you specify an automatic background dropout for color and grayscale images, but it usually does a very crappy job around the edges.
The correct way to accomplish this is to create a clipping path in Photoshop. You can try creating a path using the magic wand tool (select all the white areas, inverse the selection, then convert the selection to a path), but expect mediocre results. If you want to skip all that crap and just do it right from the beginning, use the pen tool to draw the path around the object. Cut into it slightly to avoid a white fringe. Save the path, then designate it as a clipping path. Then save as an EPS (some apps can recognize TIFF files with clipping paths embedded, but to be safe, stick with EPS).
--Mike