This seems the most appropriate place to post this.
No problems installing PDF24 on W7, however, the account creation email containing the account activation code gets flagged as spam by SpamAssassin.
Below is the SpamAssassin report:
========================
Spam detection software, running on the system "spam4.interdns.co.uk",
has identified this incoming email as possible spam. The original
message has been attached to this so you can view it or label
similar future email. If you have any questions, see
the administrator of that system for details.
Content preview: Welcome to PDF24, your personal online account is created.
You can now log in with your email address and password to use the PDF24
service. When you first log in you will be asked for an activation code. Your
personal activation code is:
Content analysis details: (7.8 points, 5.0 required)
pts rule name description
---- ---------------------- --------------------------------------------------
3.5 BAYES_99 BODY: Bayes spam probability is 99 to 100%
[score: 1.0000]
0.2 BAYES_999 BODY: Bayes spam probability is 99.9 to 100%
[score: 1.0000]
1.0 RELAYCOUNTRY_EU From an EU country that sends regular Spam.
3.0 RELAYCOUNTRY_IN Relayed through a country that might be a source
of Spam
-0.0 RCVD_IN_MSPIKE_H4 RBL: Very Good reputation (+4)
[88.99.38.166 listed in wl.mailspike.net]
0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record
0.0 HTML_MESSAGE BODY: HTML included in message
0.1 MIME_HTML_ONLY BODY: Message only has text/html MIME parts
-0.0 RCVD_IN_MSPIKE_WL Mailspike good senders
0.0 T_FILL_THIS_FORM_SHORT Fill in a short form with personal
information
========================
It might be helpful, if some attention is given to trying to reduce the risk of this email getting flagged as 'spam'. A simple first step would be to create a DNS SPF record for the pdf24.org domain.