Where Do PDF Files Come From?
In this hour, we will learn how PDF files always start out as something else. Maybe it is as a word processing document, or as a desktop publishing layout. Sometimes it is as a printed piece or as a fax for which no electronic original is available. All of these types of documentswhether digital or analogcan be converted to PDF files. Turning documents into PDF files makes them easier to shareand easier to archive.
Let's say that you want to distribute an employee manual electronically to all the employees in your company. You might not want to give everyone in your company access to the employee handbook in Microsoft Word format, where they can edit and delete text as they want. Converting the document to a PDF file allows you to restrict access so that the file cannot be edited. But the PDF file you want to post on your company's intranet site or e-mail to co-workers around the world is probably not the same PDF file you would send to your commercial printer who is creating the hard-copy versions of your employee manual. The differences between these types of PDF files are explained in this hour.
This hour is designed to give you an overview of all the tools you have available for creating PDF files. Each of these tools is then discussed in further detail later in the book.
In this hour, you'll learn the following:
What utilities are available for making PDF files
Why all PDF files are not the same
How to choose the best option for making your PDF files
Not All PDF Files Are the Same Quality
When making PDF files, it is important to consider how they will be used. Are they going to be sent as e-mail attachments or posted on a Web site? Are they going to be given to a commercial printer for high-quality offset duplication? Maybe they are just going to be used around the office and printed on laser printers.
Knowing how a PDF file will be used allows you to select the best way to create a PDF that will meet the needs of the recipient. If you post a PDF online that was designed to be sent to a commercial printer, the file will be much larger than necessary and take a long time to download. If you send a printer a PDF that was designed for posting to a Web site, the colors in the file might not print accurately and will not look as expected. The settings used to create the PDF file can change the appearance of the PDF file, as you can see in Figure 3.1.
Figure 3.1 Graphics in PDF files look different based on how the PDF file is created and which settings are used when making the PDF file.
Posting PDF Files on Web Sites
PDF files posted on Web sites should be designed to download as quickly as possible and to look good on the recipient's computer screen. To make these PDF files look good on-screen, save them in RGB (Red Green Blue) color modethe same color mode used on all computer displays. This mode provides for more vibrant colors, but these colors cannot always be reproduced when printing. Also, the RGB color mode takes up less space in the file than the mode used to build PDF files for printing.
To allow your PDF files to download more quickly, the resolution of graphics in PDF files that are posted to Web sites should be set to the same resolution as most computer monitors: 72 pixels per inch (sometimes referred to as dots per inch, or dpi). This resolution makes graphics look fine on a computer screen, but they will not be of a very high quality if you have to print the file. The resolution of graphics is separate from the resolution of text; creating a PDF with low-resolution graphics helps reduce the size of the file, but the quality of the text is not affected.
To further reduce the file size of PDF files that are posted on the Web, it is a good idea to remove the fonts from the file. You don't have to worry that your document will look different after you have removed the fonts because all versions of Acrobatincluding the free Readerinclude font substitution technology. This technology allows you to remove the fonts from the PDF file while being assured that the person who receives the file will still see a document that matches the intent of what you created. Your line breaks will not change and no pages will be added or deleted because of text reflow. PDF files always look the same on all recipients' computersregardless of the platform they are using and regardless of the fonts installed.
Use the Web settings for PDF files that will be sent as e-mail attachments. This keeps the file size small and makes the files easier to send and receive.
High-Quality PDF Files for Printing
Most commercial printers love to receive PDF files from their clients. They know what you want your file to look like, and they have no concerns that what they print will not match what you intended. They can take your PDF file and output it on their specialized, high-resolution equipment. However, there is one warning: You must create your PDF files for printing differently than those you create for posting to a Web site or for use around your office.
Your printer will want a PDF file that includes all the fonts you used when the piece was designed. Including the fonts in the PDF ensures that the file the printer receives is an exact match to what you creatednot just a very close resemblance. Although PDF files created without including the fonts can look pretty similar to the original (it may take a magnifying glass to see the difference), printers are much more particular. The graphic arts industry wants an exact match, so your printer will require a PDF file with all the fonts included. Including the fonts in the PDF file makes the file size larger; this is the trade-off for creating an exact match of the original. You can see how including the fonts in the PDF makes the file less desirable for online posting, and why you want to create different types of PDF files for different purposes.
The colors used on a printing press are different than those used onscreen. Printers use CMYK (Cyan, Magenta, Yellow, and Black) for printing. The colors used in a PDF that is sent to a printer should reflect this fact instead of using the colors used for on-screen viewing. Using CMYK colors for your PDF file will make the colors appear more muted, and not as attractive on-screen. This also increases the file size slightly.
PDF Files for General Office Use
PDF files that will be used around your office, printed on laser printers, and posted to a company intranet site (which is typically faster than an Internet site) should be of a higher quality than those posted to an Internet Web site, but they do not have to be as high-quality as those being sent to a commercial printer. The primary difference between PDF files that are sent to a commercial printer and those created for general office use is the resolution of the graphic files. Both office-quality PDF files and print-quality PDF files are converted to CMYK color because office printers also use these colors for printing. PDF files for both these purposes include fonts to ensure consistency and accuracy when printing and viewing. But the graphic resolution for office-quality PDF files is about half of that used for commercial printing purposes.
PDF Files as eBooks
PDF files that will be distributed as eBooks are files that can be launched in an electronic software program. They should be of a slightly higher quality than PDF files that are used for onscreen viewing only. eBook PDF files also embed all the fonts used in the original file, ensuring that the eBook readers get an exact representation of the original file. The higher resolution and the inclusion of fonts creates a slightly larger file size.