If the PPT slide is in A4 (but the cm sizes are wrong)
and then we covert it to PDF it still says that it is
size A4 (no centimeters given) but it is a different size
when you print it or just view it on the screen to the
other pages (like from Word or Excel). It is PPT 97 and
Acrobat 5.0, if that makes a difference I don't know.
For starters, if you don't already have the Acrobat 5.05 update (free) it'd
be a good idea to get it from adobe.com
Next, Acrobat 5 has a habit of cropping stuff from PowerPoint. To see if
this is happening, open the PDF in Acrobat (not Reader) and choose Document,
Crop Pages. See if any cropping is set - if so, click Set All to Zero and
choose all pages. That might be all it takes to kick the pages back to the
same size as your other PDFs.
Also, the standard page sizes in PPT tend to be not the real paper sizes (or
proportions) but something that matches screen proportions and will fit on
standard paper sizes. Result: your slides may have larger white margins
than the docs you print from Word and other apps.