Do I need one Paddle account for each of my websites?
This is up to you - and it depends on what you need
One account for all businesses
You can sell all your products and services from one Paddle account, but please note that some settings are global for the whole account and can’t be customized to individual products.
Per account, it is only possible to set:
one legal name
one display name
one tax setting (tax added or included in price)
one bank statement descriptor
one set of metrics and reporting data
That being said, you can use the 'referring_domain' parameter in the Paddle.js implementation to indicate which website a sale is coming from. This data will then be included in webhook alerts and reporting so that you can filter by this later if this is sufficient for you.
TL;DR - yes you can, but this might make it tricky to keep your businesses separate in reporting and accounting.
Separate accounts for each business
This option will make it easier for you to keep the data from each business separate, and to have different settings for the various businesses. The only downside to this is that you will need to create a new account with a unique email address for every new business.
TL;DR - a more tidy and flexible option, but necessitates maintaining two separate accounts.