Salesforce CPQ Document Generation Loading Indefinitely

When additional documents are included along with the generated document, each file is loaded, converted and sent out to the Heroku server with the request body. When the request contains a large amount of data there is a potential to encounter Apex Heap size errors which can be seen at around 12MB. In the case of an indefinitely loading dialog the debug logs will contain a heap size error which may not be displayed to the user.

Heap size cannot be increased since it is a governor limit. The solution is to decrease the size of the attachments for the document in question. The additional attachments can include documents that are part of individual template sections regardless of whether these sections have conditionals. These conditionals only apply when the document is rendered therefore every attachment that is part of the template will be loaded when the document is being built.