If you choose to publish your app to Apple's App Store Connect and you happen to offer paid subscriptions, then there are 3 options that you can add in your subscription set up that might appeal to your readers.
The three Introductory Offers are Free Trial, Pay as You Go, and Pay Up Front. You can choose the length of the introductory offer based on the standard subscription duration, check out the table below, taken from Apple's website:
This is the most commonly used promotion that we see publishers use.
A free trial is basically letting your readers unlock your content for a specified period of time before their account/card is charged with the subscription price.
So their subscription period starts immediately, but they won't be charged until the free trial period is over.
Pay as You Go
If you select Pay as You Go, your readers pay a discounted price for each billing period for a selected duration.
Your subscription price is $9.99/month, but you want your readers to be able to purchase the subscription for $1.99/month for the first 3 months. In this case, you need to set up the Pay as You Go option.
After three months of paying $1.99/month, your readers will be charged the normal subscription price $9.99/month on the 4th month.
Pay Up Front
If you select Pay Up Front, your readers pay a one-time discounted price for a selected duration.
Your subscription price is $9.99/month, but you want to offer your readers a one-time special price of $1.99 for 3 months. This means that in the initial purchase, your readers will pay a total of $1.99 and unlock the subscription content for 3 months, and then they will be charged the regular $9.99 price on the 4th month.
How to Set Up Introductory Offers in App Store Connect:
2. From My Apps, select your app.
3. In the sidebar under In-App Purchases, click Manage.
4. Choose which subscription you want to set its free trial period then click on it. Scroll down until you find the + symbol in the Subscriptions Prices section. Click on that +.
5. It will be prompted to open a new page. The first page is all territories you can select for this free trial. After you select the territories then click on the Next button at the bottom.
6. You will be asked to enter a start and end date. This is not to set up the duration for your introductory offer, but to set up for the period of when you want the offer to be available for the subscription. (Example: You want to offer a Pay Up Front promo, but only until the end of 2021, then you can set up the end date to be December 31st, 2021)
You may select No End Date if you want the introductory offer to be available indefinitely.
Click Next when you're done.
7. Select the introductory offer you want to use, as well as the duration.
8. Once you've finished selecting the introductory offer and the duration, click Done. The introductory offer will be implemented to your subscription on the chosen start date.