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How effective is Adobe ifilter for extracting text from scan\image in a pdf?
does it give 100% result or it can have its own limitations.
I am asking this because we have migrated a huge set of documents from Documentum to SharePoint and it shows less number of results here, for example if it showed 200 pdfs in Documentum for a keyword XYZ, it shows 150 in SharePoint for the same keyword.
When we checked missing documents. They are present in SharePoint and crawled as well.
If the PDF file contains images instead of text, i.e. you cannot select the text using a Acrobat Viewer - SharePoint will not be able to index it even with iFilter for Adobe configured. http://blogs.msdn.com/b/priyo/archive/2006/03/02/542208.aspx . He also mentioned the workaround, i.e convert the PDF into Tiff or using the PDF write to convert the image into text.
If you have a lot of scanned, faxed or other kind of image based content then you will need to carry out a separate OCR step for best results. This will place a hidden layer inside the PDF with all the text inside.
Any modern search crawler, including SharePoint's, can then index the content of the documents resulting in many documents, that were previously un-indexable, to show up in search results.
Added bonus, you can copy and paste text, as well as search inside image based PDFs using any PDF reader.
Third party software is available to automate the OCR process using a simple workflow.
Full disclosure, I worked on such as project. For details see this Knowledge Base Article.
It is entirely based on the OCR software that created the PDF (and added the discovered text). In SharePoint 2013 PDFs are indexed natively. In SharePoint 2010 you have to add a third party. You indicate that you are using Adobe, personally I would NEVER use the Adobe PDF iFilter. You will get significantly better results from foxitsoftware.com and their PDF iFilter. It is significantly FASTER than Adobe, so your crawls will finish faster. It is SUPPORTED, and yes, you have to pay for it.
