How do I send word documents like waiver to with invoice to clients?

There's an option to attach Word documents when sending invoices from QBO, bodeebye. 

You can attach a file with a maximum size of 20 MB. Let me share these steps on how to use the feature and include the waiver when emailing transactions: 

1. Go to the Gear icon and select Attachments.
2. Click the Paper clip icon (Attachments) in the upper-left hand corner.
3. Look for the document and click Open.
4. Wait for the confirmation that the attachment was uploaded successfully.

After saving the file, follow these steps on how to add it on the invoice:

1. Open the invoice.
2. Scroll-down to the Attachments section in the lower-let hand corner.
3. Click the Show existing.
4. Select the document in the list of attachments in the right-hand corner.
5. Click Add to attach the file.
6. Click Save and send to email the transaction.

Other ways on how to use the feature are also shared here: Attachments In QuickBooks Online.

I'll be around if you have other questions when sending and managing sales transactions in QBO.