The novena in honor of the Holy Ghost is the oldest of all novenas since it was first made at the direction of Our Lord Himself when He sent His apostles back to Jerusalem to await the coming of the Holy Ghost on the first Pentecost. It is still the only novena officially prescribed by the Church. Addressed to the Third Person of the Blessed Trinity, it is a powerful plea for the light and strength and love so sorely needed by every Christian. To encourage devotion to the Holy Spirit, the Church has enriched this novena with the following indulgences:
Those who make a private novena in honor of the Holy Ghost, either before Pentecost or at any other time in the year, may gain:
An indulgence of 7 years once on any day of their novena.
Source: Novena to the Holy Ghost, Imprimatur 1948
A file with the Novena is below.