Most companies and even individuals have a scanner that can create PDFs (Portable Document Format) from paper documents. Overwhelmingly, these devices create image-only, non-searchable PDFs.

Having searchable PDF files is absolutely a must in the modern office. Dealing with text documents saved as image files is a clumsy, inconvenient process, as these files cannot be searched automatically, and lose many of the benefits of digital recordkeeping.

For this reason, you need to ensure that even your scanned documents are text-searchable and easy to read. Using Optical Character Recognition (OCR) and PDF software can add an invisible layer of searchable text while maintaining the original appearance – giving you the best of both worlds.

Who needs this format?

Many corporations, universities, governmental agencies, and other organisations have millions of pages of invaluable information sitting on storage shelves with limited accessibility. When faced with the challenge of converting these pages to digital format, the two most important factors (besides low cost) are easy distribution and an ability to search, link, and index the text.

Since much of the process can be automated, searchable PDFs allow low-cost conversion from paper to PDF, while permitting the same linking, bookmarking, searching, and indexing that a regular PDF document allows.

However, care needs to be taken with the conversion process because any OCR errors that have not been cleaned up will be seen if someone pastes text. In addition, if text does not OCR properly, searches will fail.

What’s the difference between searchable and normal PDFs?

PDF Normal – also referred to as Formatted Text & Graphics – is the usual PDF output produced from a text processing or authoring environment, such as Word, Quark, and FrameMaker. It contains the full text of the page with appropriate coding to define fonts, and font sizes, and so on.

Searchable PDF is usually produced from scanned documents. It consists of an image of the page, with the text portions of the image converted to text for search purposes and stored in a ‘text layer.’ This layer is generated through an OCR process. While the image layer will be accurate, the accuracy of the text in the text layer will vary depending on the OCR and clean-up process that was used.

Searching is done by querying the text layer for matching text patterns. If the text is found, the image corresponding to the found text is displayed, and the materials can be read in context. So, just to be clear, searchable PDF is created in two steps: (1) obtaining a page image (for example, by scanning a page), and (2) creating the text layer via OCR.

The technology behind it

Every PDF document, unlike static image formats such as TIFF, JPEG and BMP, has the ability to contain several ‘layers’ of information. First, there is the ‘image layer’. If your PDF page contains any bitmap images, their information, such as the actual image, resolution, compression method and colour depth, are included in this layer.

Then there is the ‘text layer’. With searchable PDF, the text layer includes the actual ASCII text and an identification of the text’s location behind the bitmap of the page. This means that any page, regardless of its contents, is scanned to bitmap format and not recomposed. An OCR run is then performed against any desired area on the bitmap and the results stored in the text layer of the final PDF document. The result is an exact bitmapped replica of the scanned paper page, with text information stored behind the bitmap image of the page.

The OCR process required to create searchable PDF typically provides text accuracy of 97- to 99%. One to three wrong characters for every 100 may seem like a lot errors, but this is not a problem for those applications that this approach is designed for.

Since the user sees a scanned image representation of the original paper page, OCR errors will not be visible to the eye. The errors are only an issue when searching or copying text, which accesses the hidden text layer. If a higher accuracy level is desired, the document will have to manually proofread and corrected.

The benefits

Finding information quickly via searchable PDF files may be the most important aspect of a paperless office. Space savings and reducing paper use are the benefits that come to mind with digital filing systems. Once your paperless office is in place, you will not be able to live without searching your files at work or at home the way Google searches the Internet.

A document created as a searchable PDF offers the best of both worlds – an exact replica of the original document that is also fully searchable. You can create searchable PDF files very easily with the help of the right hardware and software.