All of our PDF Generation Tools have an upper size limit to performing OCR or Text Recognition.
Here are best approximations for the upper limit ranges for various tools:
Autobahn: 36" x 24"
Adobe: Unknown
FoxIt: Unknown
SoftTrac: Unknown
Please continue to update this article to refine our approximations. If you find a PDF that failed to OCR smaller than the size listed above, update the range. If you find a large PDF that failed to OCR for some other reason document it.