i opened a document in libre office and added text to it.i had to use 66 points to make it look like the other text that was on the document.when i come to print it only has a part of the doc in large size print
EDIT by @Hrbrgr: yelling out.
Besides the fact that using all caps is considered yelling, the answer to the question expressed in your title seems obvious, if you set the font size (btw: which fonts are used in your document?) to 66 pt.
Have you tried varying the setting under View | Zoom ?
Have you tried highlighting all the text in your document and then setting the font size for it, all at once? I believe this will override any previous setting, or mis-setting, of the font size in any part of the highlighted portion.