I'd say your best bet is probably going to be an SDK Script in Workflow. You can use the script to get the exact size of each page, including text, and loop through to determine where to break it up.

The following code will iterate through each page of the document and calculate the total size so you can break the document into chunks of less than 80MB.

// Get source document
DocumentInfo doc = (DocumentInfo)this.BoundEntryInfo;

long docSize = 0;
long sizeLimit = 83886080;

// Read values of each page
PageInfoReader pageReader = doc.GetPageInfos();
foreach (PageInfo page in pageReader){
    // get total size of current page counting image and text
    long pageSize = page.ImageDataSize + page.TextDataSize;

    // if adding the new page will not exceed 80MB
    if((docSize + pageSize) < sizeLimit){
        // add to current document page size
        docSize += pageSize;
    }
    else {
        // split document
    }
}

Obviously not a complete solution, but it should get you pointed in the right direction.