I quote Wikipedia :
PDF was standardized as an open
format, ISO 32000, in
2008, and does not require any royalties for its implementation.
Anyone may create applications that can read and write PDF files
without having to pay royalties to Adobe Systems; Adobe holds patents
to PDF, but licenses them for royalty-free use in developing software
complying with its PDF specification.
The PDF associations defined two ISO standards for PDF :
ISO 32000-1 (PDF 1.7)
ISO 32000-1 is the first ISO specification for PDF. The document is an
ISO formalization of Adobe’s own PDF Reference 1.7, and is technically
identical to the Adobe document.
As with previous versions, Adobe’s PDF Reference, PDF 1.7 was (and
from Adobe.com (as is the document’s errata). By special arrangement
with ISO, ISO 32000-1 is also available at no
ISO 32000-2 (PDF 2.0)
Unlike previous PDF specifications, however, PDF 2.0 is an open
standard. Any subject-matter expert whose country is a member of
ISO’s TC 171 SC 2 can join
the other experts at the table, and help determine the nature and
direction of the world’s de facto electronic document format.
The first specification (PDF 1.7) was made open to the public by Adobe
and is free to download, free even for downloading from the ISO.
The second specification (PDF 2.0) was written by ISO members,
so needs to be purchased to download.
As a clincher, the
Adobe® Acrobat® SDK End User License Agreement says :
Adobe has a number of patents covering technology that is disclosed in
the Portable Document Format (PDF) Specification, version 1.3 and
later, as documented in PDF Reference and associated Technical Notes
(the "Specification"). Adobe desires to promote the use of PDF for
information interchange among diverse products and applications.
Accordingly, the following patents are licensed on a royalty-free,
nonexclusive basis for the term of each patent and for the sole
purpose of developing software that produces, consumes, and interprets
PDF files that are compliant with the Specification:
U.S. Patent Numbers:
In addition, the following patent is licensed on a royalty-free,
nonexclusive basis for its term and for the sole purpose of developing
software that produces PDF files that are compliant with the
Specification (specifically excluding, however, software that consumes
and/or interprets PDF files):
U.S. Patent Number:
These are the only patents on PDF, still held by Adobe,
which had released them for royalty-free public use, which includes
the ISO as member of the public.
However, Adobe remains as the only patent holder.
I have also managed to find the first pages of the
PDF 2.0 Format Specifications,
which contains a copyright notice :
© ISO 2017, Published in Switzerland
However, that document also has this paragraph :
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will
be in the Introduction and / or on the ISO list of patent declarations received (see www.iso.org/patents).
I have downloaded this list of patents which might affect this document,
and I note that not even one of them belongs to the ISO.
In fact, the ISO does not request patents, only publishes standards.
So the situation is currently : Adobe holds patents that are free for
public use. ISO had published a standard for PDF 2.0
that is a superset of the PDF 1.7 standard, so is still subject to these
Conclusion : The ISO holds copyright to the document, but not any patents.