When a user opens a protected PDF document the Viewer checks to see if the decryption key is available. If it is not present then the Viewer checks with the administration server to see if the user is authorized to view the protected PDF.
If they are, the decryption key is transparently relayed to the client and the protected document opens.
DRM controls are enforced by the Viewer software. Safeguard protects PDF files from printing — it disables printing of PDF documents by default so you do not have to apply any additional controls to stop a PDF being printed. As well as using Safeguard to stop PDF printing for specific or all documents, you can stop printing on a user basis — you can disable PDF printing for some users but allow printing for others using the same protected document you only have to protect the document once for all users rather than on an individual basis.
Documents can be protected with zero prints available to stop PDF being printed and then individual users can be granted print rights by altering the number of prints available. If you allow printing, you can limit the number of times a PDF can be printed by each user in order to stop users distributing high quality copies of documents to others. Document watermarking is recommended if you allow printing to discourage photocopies being made — see PDF watermarking below.
The important issue is not whether you can stop a PDF being copied but whether the recipient of the copied file can use it.
If you encrypt a PDF with a password you can give a copy of the PDF to another user along with the password and they can use the file. So the protection provided is worthless as a useful copy was made that could be used with others. Safeguard effectively stops PDF copying because a copy of the protected file is of no use to another user without the decryption key to open it. Decryption keys are stored encrypted in a keystore which is locked to the device it was registered on — so only authorized users can open protected PDF files.
Authorized users must be prevented from saving the PDF in unprotected format so no editing or saving options should be made available and unprotected files should never be stored on disk in temporary files where they could be easily recovered.
For additional security the PDF Reader should prevent screen grabbing, and document owners should disable printing so photocopies cannot be made of printed documents. If you are going to stop document sharing and editing then you have to stop Save As from being used so PDF documents cannot be saved in unprotected formats. The simplest way to do this is to not have the facility available to begin with. Some products use JavaScript to disable the Save As menu item or short-keys, but JavaScript can be easily removed or turned off in a browser environment and so cannot be used securely.
The only documents that can be copied are protected PDF files and they are useless to unauthorized recipients as they need the correct decryption keys to open them. You might want to think again.
The way every browser works is by caching information to disk. And browser environments are possibly the least secure of all because if no software is installed on a device then you have no control over the actual environment so stopping screen grabbing and printing to file drivers is not possible. See Secure Downloads for additional information on stopping downloads and copying.
To stop the browser caching the PDF on the users system, they convert your PDF files to images when you upload them — so the document is no longer a PDF file but consists of just raster images. However, this provides a poor user experience since images are slow to display and print, and features such as search, bookmarks, and annotations are unlikely to be available.
However, if you encrypt a PDF file and the user does not have the decryption key to use it then it does not matter if they can download it. And if you apply DRM and licensing controls then authorized users those given access will be restricted as to what they can do with downloadable PDF files for example not being able to share them with others. Many cloud based systems claim to stop PDF forwarding — however users can share their login credentials with others so they have access to your documents anyway.
If a system uses document links then there is nothing stopping an authorized user emailing those links to other users along with the login information. Some systems state that they lock PDF files to email addresses or domains but that just means that you have to login using that email address or any email address that belongs to the domain.
Switch to One of these 7 Alternatives. Affiliate Disclosure: Make Tech Easier may earn commission on products purchased through our links, which supports the work we do for our readers. What is a PDF? Is this article useful? Yes No. Never Miss Out Receive updates of our latest tutorials. Sign up for all newsletters. I would like to receive newsletters via email.
We will not share your data and you can unsubscribe at any time. Tracey Rosenberger Tracey Rosenberger spent 26 years teaching elementary students, using technology to enhance learning. Comments 4. Facebook Tweet. Jul 17, at am. In this case the steps are:. For more information on providing print security and other DRM-enabled facilities, please contact us. A little background should help clarify this. With the introduction of screens for interacting with computers in the s it was necessary to provide dedicated hardware components to manage the display of text and graphics.
The cards and chipsets included both processing and memory handling functions, and software tools soon became available that would access the stored information directly. The user did not need to understand where this information came from, just that it was readily accessible. The operating system was essentially bypassed by the screen capture software, which could go straight to the hardware memory to read the information that was displayed visually on-screen.
To prevent such programs from being used to capture screens mechanisms had to be found that interfered with the way they worked. The principal mechanism was to identify that a process was running that was known to have screen capture functionality, and then to refuse to display some or all of the screen until the offending process program was terminated.
This worked fine for some years, until new devices, operating systems and ways of working were introduced in the last few years. With the introduction of mobile devices tablets manufacturers quickly realized that many customers wanted to capture screens for onward processing. This hardware-based screen capture facility meant that information display, such as a PDF on screen, could always be captured and no software mechanism could prevent it.
In parallel, more advanced versions of desktop operating systems from Apple and Microsoft started to include screen capture software as standard, running in a background thread or process, that end users were completely unaware of.
These changes to the hardware and operating system environment have meant that mechanisms to prevent screen capture either no longer work in a cross-platform world or create more problems than they solve. However, limited scale protection is possible for specific operating systems, notably Windows variants, where systems such as Javelin now incorporate some quite clever procedures for preventing screen capture if this option is specified for secured PDFs.
A further development has been the introduction of much higher resolution screen displays. Until very recently all computer screens were less than dpi dots or pixels per inch.
This compares with typical print output which is at least dpi, and high quality print and image data which is dpi. High resolution screens require far more memory and processing, which is why they have only started appearing in the latest range of tablet and mobile phone devices e. The only workable cross-platform solution to such issues is to add static and dynamic watermarking to secured PDFs.
This information then forms part of the in-memory and on-screen data, and as such will always be included in any capture process, and can be difficult or impossible to remove. It is even possible to include invisible watermarks, using special characters or hidden graphics. The use of watermarking is discussed in another of our blog entries — please see here for more details. The first is the displayed information is essentially just a graphic image, rather than selectable text — there is no facility for text selection nor any support for the clipboard i.
The second is support for static and dynamic watermarking, as discussed above. Finally, recently enhanced, there is the screen capture protection option. If you have any questions regarding this blog item, do please contact us or add your own comment to this entry.
But as they go on to say:. Changes like adding a password can only be applied to Adobe PDF documents. We can handle them all. You can also upload other files types like Word docuemnts and images. We will convert them automatically to PDF and apply the passwords. But there is more!
You are not restricted to work from a computer. We make it possible. Rate this tool 4. You need to convert and download at least 1 file to provide feedback. Feedback sent. Thank you for your vote. Edit a PDF file. Improve PDF files.
0コメント