Whilst it is not usual to paint paper, it may on occasions be found desirable to do so, eg. overpainting of wallpaper, liningpaper, etc. “Oil-based” paints should not be applied to paper because they harden and embrittle progressively with age.
Wallpaper adhesive remains water soluble and the paper would automatically bubble due to expansion and softening of the adhesive when overcoated with water based paints. These bubbles usually disappear when the paint dries.
Dust off. Ensure that the paper is adhering firmly.