adjusting bleed box to zero when opening a file

Even better, you can automate preflight with a script on a toolbutton or menu item, so you don't have to open preflight all the time. 

Just a note on page boxes. There are some printing machines that require the Trim( or Bleed maybe) to have an origin a zero, which push the crop to have a negative origin. This can be set from JavaScript, but it won't work out the way you might think, because changing the crop changes the view on the screen without automatically adjusting the other boxes. Since JavaScript always puts the crop at zero, a negative interal crop will affect setting the other pages boxes in unhappy ways. This also screws up all of the markup annotation coordinates.  This is a printing only setup and should only be done with a print oriented tool like preflight or the other Callas tools.   

I'm guessing you need to add the bleed to the page size, for example, you want to change an 8.5 x 11" page to 8.75 x 11.25", removing the bleed box?

You can use a Preflight fixup to change the art, trim, bleed, crop & media boxes (Tools> Print Production> Preflight> Fixups). Select an existing fixup and duplicate it from the options fly out menu (you need to duplicate it, as you can't edit an existing fixup). Rename and save it after you have it working as desired. You can add it to an Acrobat action and quickly apply it to a file, or a folder of files. You may need to export it to your desktop, then re-import it, in order for the Action Wizard to see it.

To zero? That doesn't make much sense... Do you maybe mean to the Crop box?