Upvote:3
As stated by Timatic, the database used by airlines
Residents of Italy holding expired Residence Permits or a copy of an expired Residence Permit are permitted to re-enter Italy, provided also holding a receipt issued by the Italian Post Office or Police Department, confirming new permit has been applied for. Applications for renewal must be made within 60 days of expiring, otherwise immigration could refuse re-entry, even if holding confirmation of application. Holders copies of an expired Residence Permit also require a statement, stating that they are holding a copy.
Since you're awaiting your first permit, this does not apply to you.
As such, if your nationality requires a visa to enter Italy for less than 90 days, don't leave Italy until you've received your permit. If you're already abroad, contact the Italian embassy where you are immediately.