I'm guessing this may be a schoolbook edition of a 'normal' serif font, but I don't know yet which one.

Interesting! I'm now curious about school book editions of fonts, and why publishers see a need for a special version for that purpose.

I'm now curious about school book editions of fonts

Older thread (with links to still older ones).

That might also be a normal font containing the unicode IPA Extensions character U+0251 (used for a) and U+0261 (used for g). Here is what the same text gives with Charis SIL after replacing those two characters.

I see that in a link above, there is a long list of fonts that could serve; in fact, even Times New Roman on my mac could do it.

Wow, IPA Extensions? This is something else that is new to me. What is it, and how do you insert one into a font?
(Thank you for the link to the previous threads on Schoolbook editions.)

IPA Extensions [...] What is it, and how do you insert one into a font?

On a mac, you can see them with the character viewer; they start at U+0250.

If you have just a few to put in some short text, you can just click on them in the viewer, like here on the script g, and it gets inserted at the cursor position. If you already have a text file, you can apply a global substitution.

That is sufficient to get a text to print, but not good to search with the Acrobat reader; if you search for "narrow", it won't find it because the a was replaced with some other character. To get a searchable text, you need a properly designed font.

I have never drawn a single glyph to my satisfaction, that's why I look only at fonts that already contain the shapes I want. Once they are drawn, all you have to do is to use some font editor to add properly named copies of the glyphs you want to use, and opentype substitution tables, to get a working font that gives you the desired shape when you type and that produces searchable texts. Such a font will work with so called "Opentype savvy" applications, like Adobe InDesign.

I should mention that there is a way to proceed without touching at the font (if the EULA does not allow modification). You need only design a keyboard layout that will give you the character U+0251 when you type "a" and U+0261 when you type "g" (there are tools for that). To search the pdf, you then need to use that very same keyboard layout.

I forgot something: if you use a modified keyboard to insert IPA characters, everything looks nice but the spell checker (in Word for instance) finds a mistake every time a word contains an IPA character.

It’s a version of Adrian Frutiger’s Apollo, available for licensing with the same wonky kerning, but without alternate ‘schoolbook’ or phonetic characters.