Changing the font almost everywhere

[Jeff Root]

I am editing a book for my friend, the author. He and his wife
typed most of the text into MS Word. It comes to about 100 pages.
After I add in the pictures, it should total about 150 pages.

I began this project over a year ago, but was interrupted by the
need to finish another book by the same author first. That book
is done and printed.

When I started editing this book I used Open Office Writer to
remove all of the existing formatting put in with MS Word. I am
guided in restoring the formatting by a printout of the text made
by the author before I began editing. That is largely complete.

Except for headings, all of the text is still in Times New Roman.
I have just decided (contingent on it working out okay) that I
want to change the font to Sitka Display, which came with either
Windows 10 or another Microsoft thing. It is on my computer.
The font will need to be embedded in the final PDF file.

I am not proficient at using Open Office Writer, and have not
necessarily used the best methods to apply styles. For example,
I put some text in boxes, and did not give those boxes a style
to distinguish them from the main body of the text. I did give
chapter headings and section headings their own styles, so that
they use fonts different from the rest of the text. Although
captions for the photos were mostly included in the text, I have
not yet put in any photos, and I will want to give the captions
a font of their own. In all, I think there are about five or six
different paragraph styles that I have used out of the very long
list built into the program, plus two or three that I created
with new names.

How should I change the font everywhere (except where I already
changed it) so as to minimize the chance of accidentally missing
anything that is still in Times New Roman?

-- Jeff, in Minneapolis

[Zizi64]

Based on the lookout of your post I suppose that you are using some old fashioned formatting methods and properties in the document.
I can guessing only witout the specific document. Please upload/share it.
My tip:
Use the most valuable feature of the Apache OpenOffice/LibreOffice: the Styles - instead of the manual (direct) formatting properties.

[Bill]

Since all paragraph styles inherit the font setting from the Default paragraph style, start by changing the font setting in the Default paragraph style. All other paragraph styles should inherit the new setting unless the font style has previously been changed in the style.

[JeJe]

In the find and replace dialog you can replace one font with another. In OO:

Make sure more options are shown by clicking that button

Click the attributes button and tick font
with the cursor in the search for and replace for boxes click format and choose the fonts you want to search for and replace

[RoryOF]

If changing the font in the Default paragraph style does not echo to the actual text, a fix is to reomve all direct formatting, which takes precedence over the style. To avoid going through the document on a paragraph by paragraph basis, typeing Ctrl M for each paragraph you can use Find and Replace.

In Find and Replace
drop More Options and select "Search for Styles"
In Find box, drop the selector and select "Default" (or whatever style the text is using)
Press Find All
Then Ctrl M.

Now all of the selected style should reflect the font and other parameters set in that style definition.