Organizing your workflow for large print jobs

Surprisingly it is not easy to find information about managing large printed file sizes in Photoshop. Here is a guide on how you should work with large printed banner size files in Photoshop CS6. There are a couple methods that each have their own pros and cons.

Note:
This post applies to raster images only (photos, etc.) and not to vector graphics (line art, text, etc.)

Method #1 - total pixel freedom

• Set the document dimensions to full size and the resolution to 150 ppi before laying out the project
• Use graphics of the correct size and resolution for your file. 150 pixels per inch (ppi) at full size (dimensions) is sufficient resolution for most posters, banners and displays. If the graphics in your project are set to a resolution above 150 ppi (at full size) either
• Resample each graphic to 150 ppi, or; 
• When saving, export the whole file to .pdf with a compression setting of 150 ppi.
• Do not enlarge JPEGS whenever possible, all that does is stretch out the pixels, defeating the purpose of having a high resolution image
• File format matters: You may be able to reduce the file size by exporting or saving your file as a .pdf (always keep the working PSD/PSB file if you want to make changes later)

• Save the file with a different name than your original file (to preserve the source file), then flatten the file (using the “Flatten Image” option under the “Layers” menu). 
• When saving as a PDF make sure to uncheck "Preserve Photoshop Editing Capabilities". Otherwise Photoshop will save a complete copy of the PSD inside of the PDF, makign for a massive file.
• Save the file as a .psd, .eps or .pdf if possible. These formats will not rasterize vector art (including fonts). Saving in other formats will rasterize the entire file, which may result in larger file size and reduced image quality

Pros: Working at 150 ppi will save you a ton of time and will still print well, original file is always preserved. You can modify pixels

Cons: It is still relatively slow to work with.

Method #2 - Duplicate guide for adjustment layers only

This next method will only allow for limited editing using adjustment layers. But makes working with large files much easier.

Duplicating an image, applying layer adjustments to the smaller image, and then scaling those adjustments to the master file. We call this a duplicate guide file.

• Duplicate the file and decrease the image size so that the file size is manageable. This is usually in the 200mb - 300mb range, which should be easily handled by most computers. This duplicated file would be your guide file.
• Apply expressive adjustments. These are layer adjustments that can be found under Layer -> New Layer Adjustments
• When you are ready to apply those adjustments to the master file you want to upscale your guide file to match the same exact dimensions as your master file. For example, in your case if you are working with a 7" x 6.483" guide file, you would then scale back to the 98" x 90" dimensions. This will cause some interpolation, but it won't be a problem because you are getting rid of the upscaled image.
• You then replace the blurry image with the image from the master file and the adjustments should be equivalently applied to the master file.
• You could then apply pixel adjustments like cropping, sharpening, etc. if you needed to. Proceed to save as outlined in method #1

Pros: You can work faster and lightweight, there is less crashes, easier modifications.

Cons: You can't modify pixels and you can only use adjustment layers. Pixels modifications must be done on the master file.

Extra tips

you should also consider your viewer in this process. From what distance will they be viewing your banner? This is a significant question because it can change the ppi considerations. As @Alan Gilbertson answered here, the suggested dimensions for a 4 x 6 meter billboard are under 30ppi/dpi. It might make sense to lower your ppi to a more reasonable number throughout the modification process. This would help your file size and workflow considerably as well. The usual professional billboard workflow in Photoshop is to build the image at a small scale with high ppi (e.g., 4x6cm @ 300 ppi), but in this case you can work full scale because you're not exceeding any of Photoshop dimension limits. It is recommended that you contact the billboard company. Either their website or their production department will give you their exact requirements for file size and format. They will have Photoshop and/or InDesign templates that not only give you the dimensions you need, but the correct color profile. Use the template. Added note: I've moved my billboard workflow to InDesign these days, and send to the provider as PDF. If you have ID CS5 I highly recommend that, for speed of production, accuracy and vastly better typographic control. real example from @Alan Gilbertson When I'm doing a "goalpost" (18 ft high by 48 ft wide with a "bleed" of 18 inches), the company's Photoshop template is 5292x2052 pixels, 17.64x6.84 inches @ 300ppi including bleed. That's 8.7 ppi at full size. The InDesign document is simpler. I did some very simple math and made it 72x27 inches, 1/8th scale. In both cases, the document uses the color profile of their Fuji vinyl printer. I keep image effective resolution over 75 ppi and we're good to go

Source: http://graphicdesign.stackexchange.com/questions/6114/pdf-artwork-for-large-posters-filesize-issues
Source: http://www.gi.alaska.edu/files/ReducingFileSize.pdf
Source: http://graphicdesign.stackexchange.com/questions/3651/what-dpi-ppi-should-a-4-by-6-meter-outdoor-billboard-be-designed-at