You can hold Shift key when draging an axis of Bounding Box to transform the element or group...so the width and height proportions are honored.
Also...you can acess the Illustrator > Preferences > General (Mac OS) or Edit > Preferences > General (Windows) and enable the field Scale Stroke and Effects. It adjust effects and strokes proportionally as you transform the object.
Let me know if it solves your problem
You may need to zoom in so that the limitations of the bounding box tool [cough]long standing bug![cough] don't affect your transform. If you are not zoomed in to the point where there is enough space to display the corner anchors of the bounding box, the bounds of the bounding box itself become the bounds of the transform! hah. It's sad and true even if it is a little hard to say.
Try turning off the preview to see whether the objects have indeed been distorted.
If not, it's the Scale Strokes & Effects pref that needs to be checked (as Gustavo points out).
If the objects are being physically distorted it may be Align to Pixel Grid that is causing it.
Scaling Stroke and Effects will help if your talking about scaling a vector object. But, if you have a large raster image that you are trying to scale down, I've found that it works better if you do it in smaller increments to allow Illustrator to deal with which pixels to drop more easily... So, instead of dragging it from, say, 3000px wide down to 300px wide directly—go to down in 20-25% increments.
If you can, post a BEFORE and AFTER screencapture here so we know what you mean by "distorted"...
>>So, instead of dragging it from, say, 3000px wide down to 300px wide directly—go to down in 20-25% increments.
Should not. Can you show a test file where you reached this??
Because when you work with links then what you are resizing is just a representation of the image. And if you are having this problem with embeded images then this can be a bug.
Thank you a lot
Sorry for the false alarm Gustavo, this information came from one of my designers. We had just been discussing this for a project we were doing, incorporating some stock photography into a poster. I relayed your response and he corrected me too - he said it's when scaling UP that an image starts losing its fidelity (naturally) and going slowly allows (in layman's terms) the invention of similar pixels to fill the gaps. Thanks for checking me on this one.
My bounding box doesn't show on any page; only the 4 corners of a placed or drawn object, or the lines on which text are placed. To scale, I have to use the Free Transform Tool, scale, then go to to Selection Tool to continue. Why doesn't the bounding box show when I use the Selection tool to begin with? This just started happening. Rebooting several times hasn't corrected it.