Do you prefer audio or text content?

I think your great content would be better positioned in a blog on your website. With the PDFs you loose on valuable organic search traffic.

Also personally I don't like to read PDFs, because I oftentimes loose the position I left off or can't zoom the text to my liking. I'd only go for PDF if the design is heavily branded or you need a specific and complex layout (e.g. strong artistic side). From looking at the latest issue I think that you could easily adapt the PDF's design to HTML/CSS.

With this strategy you could also see which articles are the most popular (visits + time on page) and then convert those into audio format. That way you concentrate your limited time only to the articles that are most relevant to people.

I prefer text because I can only listen at about 2.5x speed but I can read at more like 10x.

Audio. No time to read PDFs.

I think audio content is useless until you are able to build a following. Anyone can start a podcast, but no one will listen to it unless you provide value.

I think it's easier to promote text content because at least then it's skimmable. Podcasts (or other audio content) require quite a bit more attention than reading, and they can't be SEOed.

For me, that depends on the type of content. I like fiction and non-fiction audio-books for my bike rides to work and for doing chores. Text is best for blog posts or shorter non-fiction stuff because I can more easily look over the document if it is worth my time. Reading a text is also usually faster than hearing it, even with higher playback speed.
After looking at your PDF I'm sure that I'd prefer to read it, so I can quickly go back to parts I want to revisit. Also, some of the lists in that document are great for a visual format.
But I would certainly try out an audio format if it exists.

start with text. Text is searchable. I can read faster than I can listen.

Then give audio if they would be listening while doing something else.

But start with text.

Omnichannel marketing is the way to go now. Do all and every format you can. You want to reach people where they hang out. Don't forget youtube as well.

Always text for me. I like ebooks over regular pdf though because they work nicely with my phone, but pdf is okay.

At the risk of being trivial, both. It depends on the content (do I need graphics?) and timing (I can listen to podcasts at the office but probably can't read long documents. At other times, I want to text content, e.g.: when I'm in bed, waiting in line at a grocery store, etc.

I'm personally not much of an audio guy. I don't listen to podcasts and only really did audiobooks when I was going into an office. Music all day every day though.

With that, if your users are asking for these things, then go for it. Otherwise, may be worth holding back on it for a spell.

I primarily read on my Kindle and based on that, one suggestion I would have is to make it super freakin' frictionless on the aforementioned device: https://www.amazon.com/gp/sendtokindle/developers/button

As I typed that (and signed up for your service) I realized that I could probably just subscribe to newsletters using my kindle email address. The big fear there is the spam implications from compromised lists / list sales / bad actors in general. So yeah... send to kindle button :P