To print multiple business cards on Letter or A4 sized sheet stock:
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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.
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Set the paper size of your iStudio Publisher document to match the sheet stock size.
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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.
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Create one copy of your business card/label design.
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Select and group together all parts of your business card/label design, so that it can be selected and arranged as a single object.
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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).
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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).
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Print.
TIP: Print out a test copy on plain paper to check the card/label positioning before using your Avery sheet stock.
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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).