Don't forget with print the most common method of distribution is via the "sale or return" method, so your print run of say 20 000 copies goes out on the 15th of the month to the distributor network, is on the shelf till the end of the next month ( for a monthly mag, longer for things that are quarterly or every 2 months) and then you get either a return of unsold copies, or a statement of scrapped copies around a month later, along with the sales figures for the ones sold, and the money for them less shipping costs and invoicing costs. Thus your income is generally 3 months behind the sale, and you can lose up to half the sale to returns.
Even worse for international sales, where you can have a 3 month shipping delay for the issue, and then another 3 months in the foreign country before you get even a statement of sale. Subscribers are slightly more lucky, you at least have a good idea of the number of sales, and while you do have to package them individually ( and if you are lucky you also choose a posting country to get a cheap rate, which is why your Elektor magazine is postmarked Schipol Airport, even if it was printed in the UK) and label them, plus sort per country as well, you at least have the money either 3, 6, 12 or 24 months in advance, in most cases non refundable as well.
The PDF versions is generally the best option for international sales, no cost above your server cost for the website, and slightly more for a CDN that handles the subscriber login and tracking the downloads per user to reduce piracy, often by either watermarking the PDF file itself, or using a (barf!) flash player on line. For a publisher with large numbers of international customers this is a very big customer base, and having no dead tree editions is a big cost cutter, as international magazine post, though cheap for the mass, is not a low cost item when you are driving a 10 ton truck to the post office a few times for different destination cut off points.