Take this field and resize it to be much taller than you expect to ever need. Since this can be a pretty radical change to your layout, you may want to use a copy of your current layout and use the original layout for data entry while you use this layout for printing.
Now select this field and use the "sliding and visibility" section of the Inspector's position tab to specify "slide up" and "resize enclosing part".
In preview mode, when you print, or save as PDF, you'll see the field shrink to the minimum size needed to display the text entered into it and, if set up correctly, the rest of your layout will also slide up and resize to remove any blank space on your layout created by the size change to this field.
Key facts about sliding layout objects:
- It's only visible in preview mode and when you print/save as PDF...
- All layout objects below and in the same layout part as the slide/resize field need to also be set to slide up and resize.
- Objects in headers and footers will not slide.
- Portals will shrink/slide to fit the number of rows of records, but fields within the portal row will not shrink/slide.
- Consistent side borders are difficult to achieve with sliding fields.