réponse de Blurb support :
Blurb's ICC profile is designed specifically for use in CMYK supported applications such as Adobe Photoshop. Lightroom does not support the CMYK color space, so our profile will not appear in the ICC profile list and so it's not possible to softproof within Lightroom 4.
You may want to check out our recommended workflow to soft proof images using Photoshop
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