Is there a way for subscribers to partially unsubscribe?

Welcome to the community @MattOlen 

I’d approach it this way:

Add a muti-check box on your email subscription form for your list with the two content types - newsletter and offers - that you want as options. Push those to a custom property e.g content_preferences. You can add this as an optional 2nd step on your form, after they’ve added their email address (1st step), so you don’t impact opt-in conversions. Contacts can therefore add their preferences during subscription opt-in when they’re most engaged.

For your campaigns, add the same muti-check box options pushing to the same custom property (content_preferences) to your email preference page https://www.klaviyo.com/email/pages/preference-pages/ . You can link to this page in your emails using {% manage_preferences %} and ask them to state their preferences. 

You can then use the custom property values in sending segments for your email campaigns (and as display show/hide logic). 

Not every contact will update their preferences. And from day one, all existing contacts will have nothing in their content_preferences. So to ensure you hit all the optin contacts while respecting those who have selected their preferences, I would assume the following in your sending segments: 

• if an optin contact has no values in their content_preferences, send them both newsletter AND offer content. 
• If an optin contact has set one or both values (newsletter and/or offers), send the appropriate content.

Does that help you?

Regards

Andy