The 25-year-old, who spent five successful seasons with St Neots Town between 2010 and 2015, has arrived at The Jakemans Stadium via brief spells with St Albans City and Biggleswade Town earlier in the campaign.
Hilliard netted 73 goals in 245 appearances for the Saints and played under Dennis Greene’s management for some of his time at Rowley Park.
He began his career at Rushden & Diamonds during their Football League days and subsequently spent loan spells with Ware, Hemel Hempstead Town and Banbury United.