Usage of stock photo in a press release

I think in such cases it is better to use another royalty free images service. Because press releases are equated with the media, this is not the same as using images for personal use.

Hi, somebody from Adobe to reply here? 

I found a situation that your licence does not cover or is not clear enough for press releases and nobody from Adobe to come up with a better explanation?

OK but what if the media extract the image or screenshots it, use it to convey the message of our press release, but then reuse the image for other purposes for other articles for which we are not aware of?

It's not our fault if they do that. But the licence owner may come AGAINST US with all kind of arguments such as: you didn't protect the PDF against copy, you didn't make a low version of the image on your website, etc. 

I see only one thing to do in that case: to include a note in the press release explaining that the media can not use the photo illustrating our press releasde. 

Generally speaking: Press releases are supposed to be published by the media. So, you should make it clear, what can and cannot be used.

I suppose you acquired the asset under a standard licence:

3.1. b (iv) you may not use, reproduce, distribute, or display the Work with a press release that includes the distribution of the stand-alone image file to the media.

In this case, you seam to be OK, as you distribute all as a PDF. But media wants to publish often the illustrated press release, and you should make this possible in your own interest. We often include pictures with our press releases where we state that they have been cleared for publication with the release. This would need you to buy an extended licence:

3.3 a (iii) a press release, including distribution of the stand-alone image file to the media, if the Work: (A) is only
published in connection with the press release, and (B) is not used or disseminated in any other manner.

This would mean that media can use the asset to publish your press release, but can't use it for other purposes, including publishing press release unrelated stuff on your company.

All other use would imply that the media has acquired a licence on its own for this media.

Look here for more information on licensing: https://community.adobe.com/t5/stock/links-for-licensing-terms/td-p/11366788
(Disclaimer: As always with licensing, this is my interpretation of the rules. I think they are correct and advice is based on reading and interpreting the licence terms and on fair use for both the buyer and the artist/stock company, but I cannot rule out that my interpretation is wrong. I'm not an Adobe employee).