Some Questions on Saving PPT as MHTL files

[Alice Wei]

I have noticed that your .mhtl files is the file most likely the form of PDF.
However, I tried to save it yesterday on my Hard Disk, but some of the fonts
that were originally on my Powerpoint disappeared in the web format (.mhtl)
What is odd is, some of fonts in files disappeared all throughout the slides,
while some only a few. Do you know the reason?

I know that from your company's MS Word, you have the so-called that when
things turn into web-format, some elements would disappear. Is this the case
with what is happening with my files? Could I do anything about it?

Best,
Alice Wei.