Sorry to this it was not possible to change the font of TTF to APK. You may not get as many fonts that you get on your PC.
Opis TTFApkConverter. This is a converter app that can convert font file(.ttf) to apk file. Important 1) It doesn't modify content of font file. 2) It just creates apk file wrapping a font file(.ttf).
There was an app which will help you in changing the fonts of the document that you are having. There are many more apps which suits to your android phone those will convert the font, fetch for thr app that suits to your phone and get it. Make that you have to install the app without any issues such the in future you may not have any issues regarding this app and the work it does. Hope this will be helpful to you.