There is no good solution within Acrobat Pro itself. However, you CAN do the edit if you also have Adobe Illustrator installed.
Open your PDF document in Acrobat Pro. Instead of using TouchUp Text Tool, use the TouchUp Object Tool. Select the line of text you wish to alter, right click and choose Edit Object.
Your line of text should open up in Illustrator. Illustrator will use a substitute font, letting you edit at will. NOTE: you will NOT be able to save your change in the original font. Good news is that Illustrator has a large number of fonts to choose from and you will most likely find one that is very close to the original - good enough for quick edit purposes.
Save your change and exit Illustrator. Your change should be reflected by Adobe Acrobat Pro. Another benefit is that your changed text is now TouchUp Text editable from within Acrobat Pro.
