An additional coat or two on a wood floor is what we used to call a 'buff and coat'. This sounds like what you need. Some of the major finish manufactures have systems for improving the adhesion of the additional coats. Bona Prep and Tykoat are two of these products. Certain contaminants such as wax or silicone which interfere with adhesion are difficult to remove completely. There is some risk that the new finish will lift if there are contaminants on the finish especially at the edges of the boards.

Sorry it should be Tykote not Tykoat

Thanks

Funny you should ask this today.

I just got done using this floor restorer on my engineered hickory wood floors and it looks fantastic. I don't know how extensive you want to go but maybe this is all you need.

Read the reviews and see what you think.

Here is a link that might be useful: Floor restorer

I would sand and refinish as some finish wont stick. I would use Waterlox. Great product and I am using it on my hickory 3/4" x 3 1/4. Looks fabulous! Its is expensive here in CA about 100 bucks a gallon, but worth every penny.