To print multiple business cards on Letter or A4 sized sheet stock:
If using Avery (or similar) sheet stock, find and download the appropriate Avery template from the Avery website, and export the template to PDF file, as required.
Set the paper size of your iStudio Publisher document to match the sheet stock size.
If using a PDF template, insert/drag the template into your iStudio Publisher document and align it with the page. The template size will usually match the printer sheet stock size.
TIP: It's best to add a PDF template to the first master page so that it's out of the way behind the business card/label content, which you should place on the first body page.
Create one copy of your business card/label design.
Select and group together all parts of your business card/label design, so that it can be selected and arranged as a single object.
Make multiple copies of your business card/label design and manually arrange these on the page (within the alignment guides provided by the PDF template).
TIP: To achieve finer positional control, you can apply small 'nudge' movements via the keyboard arrow keys to position a card/label design between the snap grid lines. You can also set a smaller grid spacing (settings available on the Document Inspector, on the Grid tab).
If using a PDF template, delete it (or move it off the page on to the canvas area so that it's handy for future reuse).
Print.
TIP: Print out a test copy on plain paper to check the card/label positioning before using your Avery sheet stock.
If you ever need to update your card design, delete all but one copy, update it and then make fresh copies (repeat steps 4-8 above).