Are there any online donation platforms that handle PCI-compliant payments and embeddable petition forms?

Yes. A few platforms combine PCI-compliant payment processing with embeddable petition or advocacy forms.

Good options to look at

• NationBuilder
  Supports donation pages, petitions, and embeddable forms. Commonly used for advocacy/campaign-style sites.

• Action Network
  Strong for petitions, grassroots actions, and donations. Offers embeddable forms and payment processing.

• NGP VAN / EveryAction
  Often used by nonprofits and political organizations. Supports contribution forms, petitions, and embeds.

• Blackbaud Luminate Online
  Enterprise nonprofit platform with donation forms and action/petition-style tools.

• Donorbox + custom petition tool
  Donorbox handles PCI-compliant donations, and you can embed a separate petition form from another tool. This is a common lightweight setup if you don’t need both in one native platform.

• CiviCRM + payment gateway
  Open-source option with donation forms and some petition/action capabilities, depending on configuration and plugins. PCI compliance depends on using a compliant gateway and hosted payment fields.

What to verify before choosing

• Whether the platform is PCI DSS compliant itself or uses a compliant hosted checkout
• Whether the petition form is native or just embeddable via iframe/script
• Whether the donation and petition data can be connected in one CRM
• GDPR/privacy options if you collect signatures and donations together

If you want, I can give you a shortlist by use case:

1. nonprofit advocacy,
2. political campaigns, or
3. general fundraising with petitions.