Place image and centre javascript??

Hello,

I'm trying to create a script (Javascript) which automatically creates a document to a pre specified size (specified within the script), places a file (usually .PDF) centrally on the document page, adds crops, saves and exports.

I've got everything sorted except the place file and centre part - and to be honest after looking through the forums I'm none the wiser. Can you offer some advice please?

The file which is placed will change each time (as will its location), so I was hoping that i could use the standard place command and use the window which comes up normally...although i've horrible feeling I might have to create something - hopefully not!....I realise this is very simple for most of you, but I'm struggling!

Thanks in advance for any help!

(on a side note, would a script made from applescript enable me to select the file to be placed in InDesign, and run everything in one click, opening InDesign etc? just wondering...)