This blog post contains general information concerning the process to prepare your PDF for print-on-demand (POD). A software-specific blog post relating to Affinity Publisher is available here. Since I’m still going through the process, this document will change as I learn new lessons.
Resources
The Six Commandments of POD
- Thou shall not exceed a total ink of 240%
- Thou shall not use CID fonts
- Thou shall not exceed 600 mb
- Thou first interior page shall be printed on the right side of the book
- Thou shall have one less page than total page count used for cover template
- Thou shall be compliant with PDF X-1a:2003 or X-3:2003 formats
Top 10 Things I wish I knew before I started
- Read the official OBS Book Printing FAQs (link). Even though I read these FAQs multiple times, I still forgot some details which is why I created this document.
- Don’t use PNGs. PNGs only support RGB and not CMYK. Use TIFFs with transparencies (if needed).
- Provide better art commissioning specifications. (See below)
- Don’t trust “Export to PDF” or image editing software (i.e., Photoshop) color profiles to make sure you are under 240% total ink. Always double check in Acrobat Pro.
- Select non-CID fonts before you start formatting/layout.
- Don’t start formatting and layout until all editing is complete.
- Quadruple check everything. Even if you have the best editor in the world, as soon as you email OBS your files, you’ll find mistakes. You should make several passes. And then, make several more passes.
- Export to POD PDF specifications early in the process to make sure everything looks as expected and that you’re within the guidelines.
- The last page of your PDF needs to be blank, because that page will get cut/overwritten by the printer. Additionally, you need to have an even number of pages (either divisible by 4 or 6 depending on book size, see FAQs). So if you have exactly 112 pages, then you need to add 1 page (113, it can be blank). In this example, the cover should be generated for 114 pages, even though there’s only 113 interior pages.
- Don’t be in a hurry to send your files. It might take OBS a week to respond, so take an extra day or two to look things over. Otherwise, every mistake costs you at least an additional week of waiting. Also, be warned that any recommendations from the printer may not take other requirements into consideration – for example, if they tell you that you need to add a page, that means you may need to add more so that the total page count is divisible by 4 or 6 and that you also need to update your cover to account for a new page count.
Bonus tip. When using Photoshop and exporting to TIFF using the correct CMYK (max 240% total ink) color profile, it is possible to exceed 240% (especially if you’re using layer effects). The only way I’ve found to fix this is to open the exported TIFF in Photoshop, convert to RGB, then immediately convert back to the CMYK color profile. This will fix the total ink > 240% and not shift colors.
Document Preparation
Pages. While some might take this for granted, but nowhere in the FAQs does it specify whether the interior pages start on the right side or left side of the book. Page 1 of your interior PDF will be printed on the right side. Pages 2 (left) and 3 (right) will be the first two-page spread of your document. Since you will have an odd number of pages (divisible by 4 or 6 and then minus 1), the last 2 pages of your document will be a two-page spread. To put this simply, for your interior pages PDF, the odd numbered pages will be on the right and even on the left.
Note: The OBS FAQs say “divisible by 4 or 6” depending on book size. However, when you use the Lightning Cover Template Generator tool, it will say “divisible by 2.” I have no idea who is correct. I’d assume Lightning is correct since they are actually doing the printing and OBS is just passing it through to them. In order to comply, I’d add extra pages in order to be divisible by 4 or 6, because that will also be divisible by 2 – and that might save you a single email back and forth with OBS which could speed up your POD process by a week or more.
Fonts. When you select fonts, be aware that CID fonts are not supported by OBS POD. Even if these fonts are embedded within the PDF, they cause problems with the printer. If you must use CID fonts, then you must export the fonts using the “Text as Curves” options for your POD PDF. Exporting as curves will increase the file size, so make sure you are within the 600mb file size limit. CID fonts are fine for your non-POD PDF, but there’s no point in creating two documents with different fonts.
How do you know a CID font from a non-CID font? Good question. If you know, let me know. I’ve found that the easiest way is to export to PDF, then open the PDF in Acrobat and look at the Fonts listed in File Properties. If you have no means to tell a CID font from a non-CID font, then export all of your text to curves and avoid any potential problems.
Images. When you are commissioning art, creating your own, or modifying art, you need to be aware of the color profile. To make things very easy, its best to always set your color profile to CMYK. Additionally, if possible, use the recommended ICC Color Profile (download at “Install and set color profiles” ). Lastly, you should know that JPEG and PNG files (along with most other files) only support RGB and not CMYK. So even if you are working in CMYK and export to PNG or JPG, then that file could causing printing issues. It’s best to save your files as .TIF files (TIFF supports transparency) using the proper color profile so that there’s no color shifting. However, even doing everything correct, your TIFF files might exceed 240% total ink (see “bonus tip” a few paragraphs up).
Recommended Image Commission Specifications
- CMYK color profile (use the recommended ICC file, if possible)
- For full page images add bleed to page size (see below)
- TIFF format with transparencies
- 300 DPI
Bleed Calculation. Outer bleed is 0.125″ and the inner/gutter is 0. For 8.5″ x 11″ page size. An interior full page image should be 8.625″ x 11.25.” A cover image should be 8.75″ x 11.25″. For image spreads, the image should be 17.25″ x 11.25″. I recommend rounding up (ex: 9″ x 12″), so it’s easier for the artist to remember and configure and tell them that that the edges will be trimmed so don’t put anything important within the bleed/cut area.
Vectors. Using vectors (aka curves) for line work such as footers and headers is typically the preferred methods and always looks better than using images. However, I experienced numerous flattening issues (X-1a and X-3a formats doesn’t support transparencies so you need to flatten your pages) when there’s a background image, vectors over the background image, and then an image with transparencies over the vectors (such as an image placed over the footer section). To fix this, I flattened my background image and footer vectors, since this was the most common appearance issue. The other vectors (such as call out boxes, arrows, etc.) are less likely to have images on top of them.
File Size Limitation
With a 112 page PDF, it is really easy to exceed 600 mb. That sounds like a huge PDF file and it is! The normal desktop PDF at 192 dpi is less than 20 mb (Acrobat v8). That’s because the required formats doesn’t support transparencies or CID fonts, so it needs to rasterize most everything and convert the fonts to curves (you can’t just pick 1 font to convert, it’s all or none). Technology and PDFs have changed a lot since 2003 (16 years ago), but the printer requires 2003 PDF standards.
It is tempting to just “flatten it all!” To make 112 flatten pages at 300 dpi which would be perfect for the printers, but that easily exceeded 2 GB! The file size limitation is another reason to export to POD specifications early in the process, so you can see exactly how large the file will become once you’ve done all of the pre-flight checks, flattening, and conversions.