Try designing a print view for your form (see
http://office.microsoft.com/en-us/infopath/HP010981031033.aspx?pid=CH011097431033).
You can remove borders on text fields by using the Format > Borders and
Shading menu item. To layout your form you can use Layout tables (see task
pane at the right in the Layout section). If you have a scanned image of the
pre-printed form, you can use this as a background image (see Format >
Background Color menu item) to layout your print view using the layout tables
I mentioned previously, and then remove the background image when you're done
designing your print view.
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S.Y.M. Wong-A-Ton