pdfpages package included in the preamble with \usepackage{pdfpages}. Within this new document the calendars can be printed in multiples with \includepdf[landscape,pages={1-4},scale=0.9, nup=2x2]{calendar.pdf}. Here, the nup=2x2 means that the first 4 pages (i.e. calendars) from the calendar document will be tiled on one page. A value of 1x2 would mean two pages will be included, one on top of the other. Another useful command is \includepdfmerge[scale=.9, nup=1x2]{calendar.pdf,5,text.pdf,1} which will print two separate PDF files on one page, in this example a calendar and some text from another document.This handy technique allows you to combine PDFs into a single document and/or compress down multiple pages to fit on one page in any configuration you might want!
