Besides the Attachments object, the Files object can receive data sent through the form as well. To set it up, just follow the steps below:
1. In the Object Mapping section of your Salesforce integration, add the Content Version object as a related object to your primary object.
2. Afterward, associate the Salesforce fields with the fields indicated in this image:
You can map the Path On Client field to any input field. However, you must associate the Content Origin and Content Location fields with Chatter and Salesforce, exactly like in the example above, while Version Data has to be mapped to a File upload field.