Catalyzes the prenylation of para-hydroxybenzoate (PHB) with an all-trans polyprenyl group. Mediates the second step in the final reaction sequence of ubiquinone-8 (UQ-8) biosynthesis, which is the condensation of the polyisoprenoid side chain with PHB, generating the first membrane-bound Q intermediate 3-octaprenyl-4-hydroxybenzoate. 4-hydroxybenzoate + all-trans-octaprenyl diphosphate = 4-hydroxy-3-all-trans-octaprenylbenzoate + diphosphate Cofactor biosynthesis; ubiquinone biosynthesis. Belongs to the UbiA prenyltransferase family.