With a document open, click File 
Print.
Click Properties, Preferences, Options, or Setup.
Click the Advanced tab.
From the Layout list, select Poster.
Select the poster size you want to print. The number you select represents the number of pages that make up the height and width of the poster.
Select Print Crop Marks if you want each page of the poster to show crop marks, which provide assistance in aligning the pages to create a poster.
Click Select Pages To Print to reprint any damaged poster pages without having to print all of the poster pages. Click pages to select or cancel them.
Click OK to close any printer software dialogs that are open.
Print the document.