Invoices in Habu always show the live status of an invoice (draft, issued, due, paid, overdue, refunded, & void) which is why we don't currently offer the functionality for your members to view and save them as PDFs directly within Habu.

However, using the inbuilt functionality of your members' browser, they can save their invoice as a PDF in a few clicks. 

Members also have access to all of their invoices directly from their own account through the User Area, though they will still need to follow the steps below to save them as a PDF.

Broadly speaking, the functionality is the same across all browsers. When your member is viewing the invoice in their browser, they go to FILE > PRINT > SAVE AS PDF.
 
However, there are a couple of variations between browsers built in Chromium and those that aren't. Here are the details for each of the major browsers that you can share with your members requesting PDF invoices:

File > Print. Click on 'Change Destination'. From the dropdown menu select Save as PDF > Save

File > Print. Click on 'PDF'. From the dropdown menu select Save as PDF > Save

File > Print. Click on 'PDF'. From the dropdown menu select Save as PDF > Save

File > Print. Click on 'Change Destination'. From the dropdown menu select Save as PDF > Save

File > Print. Click on 'Change Destination'. From the dropdown menu select Save as PDF > Save

Here's a screencast for browsers built in Chromium (Chrome, Opera, Vivaldi):

Here's a screencast for Safari / Firefox: