You cannot resize your picture directly if it is an external graphic (in FOP 0.20.5, scaling is not supported -- see [1])
However, you can try this (I have never experimented it -- take care with namespaces):
1. In your xslt, refer to your SVG document, using the document() XSLT function
2. make a fo:instream-foreign-object as the SVG container
3. transform your SVG xml as follows:
    - change width and height attribute of the svg:svg element.
    - if needed (that should be), add both viewbox and preserveAspectRatio attributes to your svg:svg element.
    - copy the whole rest of xml
Good luck (if you try it, please feed back)
[1] http://xml.apache.org/fop/compliance.html#fo-property-scaling

De : Samuel Remacle [mailto:sremacle@hotmail.com]
Envoyé : mardi 26 juillet 2005 22:57
 I'm not sure you understood my problem, the SVG should be bigger in my application than in the PDF, so as it will be first viexed in the application, I need to resize it in the XSL-FO file, and I need to keep the proportions.

So I'd like to no if there's a way to do that, does anyone know?

>From: "J.Pietschmann" <j3322ptm@yahoo.de>
>Samuel Remacle wrote:
>>application is ok. But after when I generate a PDF file from my
>>application the SVG image is too big for an A4 document. So I'd
>>like to know if there's a way to resize my SVG image keeping the
>Generate your SVG with a width and heigth attribute on your to level
>svg:svg element, both in either cm, in or pt but not in pixel (no
>measurement unit). The height and width should represent the actual
>measurements in the PDF. Use the same heigth and width on the
>fo:external-graphic or fo:instream-foreign-object in the FO source.