Because of how the PDF format is designed, it can be difficult for applications to extract its content in a structured and accurate manner. Adding to this difficulty is the fact that software that creates PDFs can write the internal data in an almost unlimited number of complicated ways.

When editing software tries to import the structure of a PDF document, it is somewhat constrained in that the PDF format specifies only what text looks like, and where it is on the page. It does not specify what that text actually is, in terms of formal style or purpose, nor does it even necessarily place things on the page in a linear or consistent order.

PDF documents also are by design difficult to edit because nothing is ever deleted from them: even tools that are able to modify/edit documents can only do so by adding new information. The old information — text, images, structure, etc. — is still retained within the file. And it can get to be a bit of a mess in there.

Additionally, some PDFs are produced by scanning a printed copy. Scanned PDFs are generally just comprised of images of the text rather than the text itself. (Unless during the scanning process the additional step of OCR — Optical Character Recognition — was taken to add an separate, invisible layer of actual text reflecting the contents of the images of text.)

Fade In is, however, able to import a wide range of PDF screenplays. But often, depending on the source of the original PDF, more or less cleanup may be required.

(There may still be a few instances where things don't work perfectly. In those cases, what you may have to/be able to do is select the text from a PDF viewer and paste it into Fade In. With that method, however, a certain amount of reformatting is almost guaranteed.)