Travelling and working in EU
For periods of less than 90 days, you are entitled to freely travel, study and work in the Schengen area without any formalities. Attention that working conditions may vary from country to country.
For periods of more than 90 days, you may be entitled to stay in another Schengen country for work, study or training provided that you are granted a residence permit according to the purpose. If so, you will have a work/study/etc. permit of stay in this second country while keeping the EU long-term residence permit issued in Italy.
Holders of EU long-term residence permit issued by other Schengen country
They are entitled to travel in Italy for less than 90 days without formalities. Nevertheless, they are required to report their presence to the local Questura.
For periods of more than 90 days they are required to apply for a residence permit to the local Questura according to the purpose of stay (study, work, etc.). The request can be submitted within 90 days.