For all Karate students and master I will post here a hundful of downloadable Karate certificates of many shapes and forms to fit all needs, you can search for them again and download them, only here you can search for them easily,  so I did and collected its information at one place.
Fake certificates of karate may be found out there, so be careful for choosing

List of Karate certificates for karate diploma students
CHINESE ARTS
JAPANESE AND OKINAWAN
KOREAN MARTIAL ARTS
KRAV MAGA, MMA, ARNIS, AND OTHER ARTS
MUAY THAI - KICKBOXING

Aikido Black Belt Promotion Certificate Kanji All Martial Arts I.D. Card Appointment as Tae Kwon Do GRANDMASTER - Taekwondo Kukkiwon Black Belt Certificate - any style - Warrior Monk
Prices of all are between ($49.95, $59.95, 69.95, and 24.95)

Bruce Lee Enter the Dragon movie mini-poster Chi Kung Kung Fu (Southern) Rank Certification - Shaolin Daito Ryu Karate Black Belt Promotion Certificate Kanji David Carradine as Kaine (Kung Fu) portrait print
All certificate cost will vary between ($39.95, $29.95, $59.95, $39.95)

GoJu Ryu Karate MUDANSHA Promotion Certificate Hapkido Kwan Jang School Charter Certificate - Hap Ki Do Japanese Judo Kodokan Diploma2 Japanese Judo Kodokan Original Diploma
Certificates on sale for ($59.95, $79.95, $44.95, $58.95 respectively)

Japanese Karate Association Black Belt Promotion Certificate Japanese Karate Black Belt Promotion Certificate Generic Japanese Kyokushin Black Belt Promotion Certificate Japanese Kyokushin Kyu Colored Belt Promotion Certificate
Certificates prices are ($54.95, $34.95, $54.95, $49.95 respectively)

Jeet Kune Do I.D. Card Karate Creed Kenpo diploma for black belt - Red Border Korean Hap ki Do Black Belt Certificate Dan Jung SMK
prices of these certificates are ($39.95, $9.95, $49.95, $59.95 respectively)

Korean Hap Ki Do Black Belt Certificate Dan Jung V1 Korean Hap Ki Do Black Belt Certificate Dan Jung V2 Krav Maga Certificate of Proficiency - Instructor Kung Fu Rank Certification 2 - Shaolin
All costs of certificates are ($59.95, $59.95, $29.95, $29.95 respectively)

Kung Fu Sifu Certification and  Kung Fu Sifu/Sigund Certification - LARGE Kung Fu Wu Shu Rank Certification - Shaolin Muay Thai Kickboxing I.D. CARD
To get these certificates you have to pay ($29.95, $49.95, $29.95, $39.95 for them respectively)

Muay Thai World Kickboxing Tournament Winner SIMTA New Kukkiwon Tae Kwon Do Advisory Committee Appointment New Kukkiwon Tae Kwon Do Black Belt Dan Jung New Kukkiwon Taekwondo 6 and 7 Dan Black Belt Promotion Diploma
Certificates sold for ($24.99, $125.95, $99.95, $124.50 respectively)

New Kukkiwon Taekwondo 8 and 9 Dan Black Belt Promotion Diploma Pankration diploma Shito Ryu Karate Certificate of Black Belt Rank Shotokan Karate Black Belt Promotion Certificate - SKIF, prices are ($59.00, $39.95, $59.95 respectively)

Shotokan karate I.D. CARD Shotokan Karate Kyu (lower belt) Promotion Certificate - SKIF Tae Kwon Do Black Belt Certificate - Chung Do Kwan Tae Kwon Do Certificate 2 Black Belt Taekwondo Kukkiwon
Sold for ($39.95, 39.95, $59.95, $64.95)

Tae Kwon Do Certificate Black Belt - Chun Tae Kwon Do Certificate Black Belt - WTF Tae Kwon Do Certificate Black Belt Taekwondo Kukkiwon Tae Kwon Do Certificate Black Belt Taekwondo Tangsoo Do
For ($59.95, $59.95, $64.95, $59.95)

Tae Kwon Do Certificate Of Appointment - WTF Tae Kwon Do Certificate POOM Black Belt - WTF Tae Kwon Do Master Instructor Certificate Black Belt Tae Kwon Do Master Instructor Certificate Black Belt
For ($59.95, $59.95, $69.95, $59.95)

Okinawa Karate league certificates:
List are previously prepared and illustrated in article about where can you find readymade Okinawa karate certificates.

kyokushin karate certificates
Only kyokushinworldfederation.org can help you get the certificates and instructions for world wide users.

Shotokan karate certificates
Global System for Shotokan Karate certificate Kyu and Dan Rank:
There are 10 Q- 10 and Dan Shotokan Karate in the world . To obtain a certificate for each rank , you must meet the certification requirements and the completion of the testing procedures . Test - or grades - and carried out by a team of trained examiners as authorized technical ShotokanWorld karate. Typically, sessions are conducted Dan grades 4 times a year , and Kyu grades will be held twice . To be eligible for the test, you must first have gained the appropriate amount of experience in the constant current rank . Then , depending on the level of Dan being graded for you , you may have to take the test outside of your country or region ( at the top of the ranks of Dan , and is authorized only Shotokan Karate global HQ to assess the grade and the issue of ratification ) .

Shotokan World Karate Instructor Qualification System certificate:
Also there are variant of certifying system in shotoakn karate as Shotokan World Karate Instructor Qualification System, Authorized Instructor qualifications (for teaching karate); authorized Judge qualifications (for judging and refereeing at tournaments); and authorized Examiner qualifications (for testing and evaluating Dan, instructors and other types of qualification). however you can obtain your copy ofSHOTOKAN KARATE CERTIFICATES KIT II; Karate certification kit with Shotokan Karate founder : Gichin Funakoshi on background, integrating belt colors and the names of the grades on a background inspired by Asian art, it is Include 10 certificates.

Karate certificates in Japanese:
Azami Press offers martial arts instructors several different options for the design of your traditional Japanese certificate. Besides choosing between a fully individualized certificate or a custom template, there are many other aspects of your document that can be customized, such as orientation, text language and layout, font, border design and color, and even the addition of logos and electronic seals.

Borders examples:
A lot of free borders found around there you can download and by simple steps of software like windows paint or photoshop you can fit one of them for your desirable certificate to award your students for karate levels or karate diplomas, examples of karate certificicate borders are: "european cool pattern vector, Ornate Wreath Vector Set, Certificate clip art style, exquisite diploma vector, european cool pattern vector, as well as some styles with Free Ornaments and Flourishes and Decorative Border by clip art shapes, also you will find certificate borders with Kung fu animals as the familiar Dragon or crane, tiger, or lion.