We observed the reflection nebula NGC 7023 at various positions using wide and narrow band photometry centred on the 7.7 and 11.3μm PAH emission features and wide band photometry at 20 and 25μm. No significant variations have been detected over the nebula in the 7.3 and 20μm continuum relative to the total emission in the 6-15μm range (hereafter {GAMMA}). This result supports the hypothesis that most of the continuum emission in both bands come from very small grains. In contrast, the 7.7 and 11.3μm PAH emission features show clear variations. We find that in weaker radiation fields of the nebula the 11.3 and 7.7μm features are not the dominant emission components in the 6-15μm range. The 11.5μm band increases whereas the 11.3μm emission feature decreases relative to {GAMMA} in the outer parts of the nebula. The effect can be explained by increased hydrogenation of PAH molecules.