Q:

How to change font size without changing the position of the text?

I have to change the size of multiple text labels in a plot, but I want to keep the labels in exactly the same position. The vertical center of each label is now aligned with a tick in the plot. 
If I just increase the font size, the size increases with respect to the baseline of the text.  This produces a misalignment of the vertical center of the text with respect to the ticks. 
To solve the problem I could create outlines of each label, but I would like to preserve editability, so this is not the solution I'm looking for.

A:

It's slightly tricky if you didn't start with centered text (which will increase from the center point when you increase the point size). You can work around this, though.

Set the transform proxy on the control panel to the bottom, right or left center depending on how the scaling needs to go and which center you need to lock in.
Increase the width and height of one label to the size you need (be sure that W and H are locked so they transform together.
Copy the W or H field value.
Select another label and paste into the W or H field, then repeat for the remaining labels.

It's a good idea when working with point text to set the paragraph alignment to correspond with the design requirement. If you'll be centering the text on some other object use center alignment, right-align inline labels, and so on. This makes the initial design slightly faster, but makes a big difference when you start tweaking.

