When purchasing a ticket from the CD website, as well as the PDF ticket in the email, there is an attachment called "instructions.pdf", which provides information in Czech, English and German.
The English wording from a purchase I made last month is as follows:
Information for Passengers
The use of eTiket tickets in inland transport is governed by the CD Contractual and Transport Terms for Public Passenger Transport (SPPO) and the CD Tariff for Inland Transport of Passengers and Luggage (TR 10 Tariff). The use of eTiket tickets to destinations abroad is subject to the Convention concerning International Carriage by Rail (COTIF), the Uniform Rules concerning the Contract of International Carriage of Passengers by Rail (CIV), the General Conditions of Carriage for Rail Passengers (GCC-CIV/PRR), the Special Conditions of International Carriage for Non-Reservation Tickets (SCIC-NRT), and the special terms and conditions of the carrier (ZUJ).
An inland travel document:
• is non-transferable and only valid in combination with a piece of personal identification belonging to the passenger whose name is printed on the ticket (any valid piece of personal identification issued by a state administrative authority, CD or other carrier may be used);
• is valid only on the day(s) and line segment for which it was purchased; it is necessary to commence the journey on the first day of the ticket’s term of validity;
• can be used in inland transport on the same day also for a different train than the one specified on any accompanying reservation issued on the same document; in case of Super-Special-Offer Ticket (SuperAkcní jízdenka), it is necessary to pay the fare difference when using different train;
• can be either printed out, presented as a transaction code, presented as part of the record on an In Karta card, or displayed on the screen of a portable electronic device (with the exception of documents containing a couchette or sleeper supplement, which must be printed in unreduced A4 format) or as an open PDF file, although inspection must be made possible immediately upon request by an authorised CD employee, regardless of the availability of an internet connection; the passenger is always responsible for the print quality or the correct display in electronic format, as the case may be;
• must not be damaged or contain illegible information, an illegible 2D code, or modified information.
An international travel document:
• is non-transferable and only valid in combination with a piece of personal identification belonging to the passenger whose name is printed on the ticket (any valid piece of personal identification issued by a state administrative authority, CD or other carrier may be used);
• is valid only for the route printed on the document, or for the route and the printed required train;
• must not be damaged or contain illegible information, an illegible 2D code, or modified information;
• must always be printed out in unreduced A4 format, for daytime trains/buses from/to Germany, Hungary, Belgium, Denmark, Switzeland, Austria or Slovakia, and for overnight trains to Switzerland, the ticket can also be presented for inspection displayed on the passenger’s own portable electronic device or using the Muj vlak (“My Train”) application;
• with the exception of separate reservations, eTiket tickets to Poland, Belarus, Russia and Slovenia are invalid if there are not printed out unless stamped before leaving the Czech Republic by a CD train conductor or at a CD ticket office (stamping except eTickets to Russia and Belarus). If necessary, passengers are obliged to actively search for a CD conductor on the train and have their travel documents stamped, or to have their travel documents stamped at a CD ticket counter prior to boarding the train;
• First Minute Europe (Vcasná jízdenka Evropa) travel documents to Poland and Slovenia cannot be returned or exchanged for reasons on the passenger’s side;
• With First Minute Europe (Vcasná jízdenka Evropa) travel documents is necessary to commence the journey on the first day of the ticket’s term of validity;
• different conditions apply to purchased reservations (couchette and sleeper).
During an inspection of travel documents, present this document to an authorised CD employee together with a valid piece of personal identification belonging to the passenger whose name is printed on the travel document. If you are claiming a discount, please also present the relevant discount card.
When returning a document purchased through the CD e-shop or using the TeleTiket service, use exclusively the “Reclamation” link in the CD e-shop; travel documents cannot be returned at the ticket counter.
More information is available on
www.cd.cz and on the information line of the CD Contact Centre, tel. +420 221 111 122.
) so eventually told me to get on and said it would be a great hassle to which I replied ok (which also went down a treat 
). 
But would have been helpful to have it more clearly marked (although lessons have now been learned). Annoying thing is I could’ve printed it off in the Ceske Drahy lounge we waited in before the train and saved all the hassle!
)
