Does a Danish furniture designer "Poul or Paul Jensen" really exist?  

no he doesn't
It's just a typical ebay trick to attract folks looking for Stuff.

wrong Stephen
See the Selig chair thread...

Poul Jensen
I'd like revive this thread and ask for proof of the existence of Poul Jensen.
A Google search for "Poul Jensen" finds only numerous second-hand attributions to this or that chair, mostly the popular Z chair. Hopefully some of my fellow Design Addicts have better evidence that he existed.

The only evidence I've seen
Is the scan of the Selig catalog pages that were posted here before.
Perhaps, that's good enough.

furnitureindex
Has Poul Jensen listed as a maker, not a designer.
No Z chair comes up though.

Update: US Patent certificate for Z chair
I thought the forum may be interested in this US patent certificate that a current eBay seller has posted with a pair of Z chairs for sale. Items of interest:
1. This is the first legitimate reference I've seen for a design date for this chair (patent applied in 1957, granted 1958); earlier than most 1960's references of previous internet listings.
2. The design with three slots on each seat rail is shown in the drawing, vs the continuous groove Fagas straps. This would indicate that the groove detail is a later design.
3. I am confused with naming convention used on the certificate: "Poul Jensen, Mobelfabrika, Haslev, Denmark". At a glance, it would appear that Poul Jensen is the designer, and Mobelfabrika is the manufacturer. However, based on my minimal understanding of the Danish language, "Mobelfabrika" does not sound like a real manufacturer, the same way no furniture maker in the US is named "Furniture Factory". I will theorize that the US Patent office misunderstood the Selig patent application, and that it was originally submitted as "Poul Jensen Mobelfabrik A/S" for the manufacturer's name only. While there is no proof of this, it would explain why you never see a documented historical reference to a person named Poul Jensen.
To further support my theory in item 3, Furnitureindex.de has listings for "Poul Jensen" as both manufacturer and designer. However, the only designer reference is for the Z chair, and is from Rago Auctions, which cannot be too sound a reference for Danish origins. No Z chairs are shown under the multiple Poul Jensen manufacturer references. However I did notice that one of the easy chair designs, by designer Peter Hjorth, has similar arms as the Z chair, albeit definitely clunkier.
My personal summary conclusion is that all Poul Jensen references to being the individual designer for the Z chair in the US was based on a US Patent misunderstanding between designer and manufacturer, and that the actual designer him/herself is not correctly documented anywhere in the digital realm.
Any thoughts?
http://ext.kb.dk/F/KAQUX2CMT2RNLD5LTJ2UENL1NBS6UEMNA667T92QRNH2I3XQ9L-36...

The only mention of Poul...
The only mention of Poul Jensen I have seen, other than this document you have posted, is in the Selig Catalog, for the Z-Chair. I have always found it interesting that the back slats for the Z-chair appear to be the same as those used on a number of Kofod Larsen chairs, albeit with the slats inverted.

Correct,
. . . the Selig catalog photo is often referenced as showing that Poul Jensen is the designer. However given that the US patent certificate to Selig indicates the same, there would be no reason for a Selig catalogue marketer to dispute that. In the 50's, communication between the US and overseas was very sparse; obviously no e-mail or internet, but phone calls were also very expensive then. I could easily see a mistake like this being accepted, perpetuated, and becoming assumed fact.
I am not claiming that someone named Poul Jensen did not exist, and it would be very believable that he headed up a "Poul Jensen Mobelfabrik" company. However, that does not automatically put him in the role of designer for pieces that came out of his factory.

I have long been curious...
I have long been curious about the relationship between Selig and Kofod-Larsen, and the manufacturers in Denmark who produced the furniture that Selig imported. It probably would not have been hard to answer the question about Poul Jensen just a few years ago, when Kofod Larsen was still alive. Robert Wexler, of Selig, also died a couple of years ago. I think that Kofod Larsen deserves having some scholarship devoted to him, and I hope someone in Denmark is working on a book about him. As far as I know there is very little information out there about him that is in print, and I have only ever seen one tiny little photo of the man himself.
http://www.furnituretoday.com/article/532080-Robert_H_Wexler_former_pres...

I noticed this vintage Selig...
I noticed this vintage Selig magazine ad online, which cites Kofod Larsen as the designer of a table that one often sees attributed to Poul Jensen.

Nice find.
Although if Selig did indeed incorrectly attribute the Z chair design to a manufacturer rather than a designer, I would be less inclined to believe any of their other advertising attributions.

Wow, these are the chairs I...
Wow, these are the chairs I have in my living room. Attributions I've found in the past have been all over the place and never a mention of Kofod-Larsen. This is the most solid thing I've seen, Thanks!

This ad shows a couple of...
This ad shows a couple of different cane backed chairs, also cited as Kofod Larsen, along with a sofa by Finn Andersen. These ads are cited as being from 1959 and 1960 magazines.

Another page said to be from ...
Another page said to be from a Selig catalog, again citing the designer of the Z-Chair being Poul Jensen. It still certainly would not surprise me if the chair is actually Kofod Larsen, but so far it has been hard to prove either way.