Transmission fluid leak 98 Ford F-150

Just purchased a used 98 Ford F-150 with 100k miles. Six cylinder, automatic. When I test drove and monitered over a few days prior to purchase, there was no sign of leak under truck. Parked in garage a few days, then started and drove. Noticed some tranny fluid leakage on floor. Fluid is like new, not burnt, no particles. Does not drip when in use. Is it simply a need to gently tighten tranny box pan bolts, or should I add some tranny conditioner to help condition seals that may expand/contract? Tranny shifts smoothly, no problems. I just want to know if this is a bad sign.
Any help/advice is appreciated. If it is only leaking when it is sitting, not when it is running, I would lean towards a tranny pan gasket. Crawl under it and see if you have one bolt that is clean as a wistle, that is probably the leaker. But nonetheless make sure they are TORQUED to SPECS. Don't just go tightening on them. You could bend the pan. ASK 79GMC1500, he posted about doing that on a previous thread.Car Repair Talk's forum.