PDF of Invoice receipts for customers. Use Shopify or QBO?

[aimeejac]

Customer needs a pdf for their accounting records of a sale. I initiated the sale via Shopify order draft and customer completed purchase through the draft invoice I then sent. But they now need a pdf, not the invoice attachment from that Shopify email. What's best method for this?

I use QBO and manually recreate all my sales there for accounting purposes. Is it best to just rely on QBO for this process or are any of you finding success using Shopify via the Order Printing App or otherwise? 

Broader question for later is about Shopify and QBO sync. I have not begun using the Integration App because my store and sales are very small still and don't seem to justify it. Perhaps integration is helpful regardless of sales volume. What do you all think?