This IDF script prompts the user for an input file of pages in portrait orientation and then shows it as double-page spreads on landscape pages.

The pages are scaled to fit the length of the input page into the height of the output page. The location of each input page alternates between the top-left and the top-centre of each landscape page so that two pages are placed side-by-side on the output page.

<?xml version="1.0" encoding="UTF-8" standalone="no"?>

<IDF UNITS="INCHES" PAPER="A4" ORIENT="L">

<FIELD DEFINE="YES" NAME="INFILE" STRING='{"Input file name"}'/>

<GROUP REPEAT="YES" FILENAME="{INFILE}">
<PAGE>
<FILE LEFT="0" TOP="0" SCALE="0.7071" PAGE="NEXT"/>
<FILE LEFT="_PAGE.WIDTH/2" TOP="0" SCALE="0.7071" PAGE="NEXT"/>
</PAGE>
</GROUP>

</IDF>