You might try heat, although I think the older Goretex was some form of Teflon. Try a small place first.

Lay paper over the spot and set a dry iron on it. If it works at all (no guarantees), you might have to adjust the heat level -- start at LOW. Ideally, the film will soften and stick to the paper like a blotter so it can be lifted off.

But here is a site that may be able to provide some suggestions (see the chart about 1/4 of the way down: Gore-Tex: An Introduction to the Material and Treatments

Sue