TechNote (Archived)

Limitations of redistilling PDF files (Acrobat 6.x-7.x)

Adobe recommends that you don't redistill PDF files (that is, that you don't print PDF files using the Adobe PDF printer or print them to PostScript and then distill the PostScript files). Although redistilling PDF files can embed fonts or reduce file size, much functionality, such as searchability and structure, may be lost.

Rather than redistilling the PDF file, try one of the following to reduce file size:

1. Choose File > Reduce File Size. This command will resample and recompress images, compress the document structure and clean up elements such as duplicate background images or invalid bookmarks. If the file size is already as small as possible, this command has no effect.

2. Use the PDF Optimizer to embed or unembed fonts, compress images or remove unwanted objects such as annotations.

For more information on these commands, read the Acrobat Help Guide "Optimizing Adobe PDF files."

Consider the following limitations before you redistill PDF files:

-- Text formatted with fonts that have custom encoding may become unsearchable.

-- Transparency is flattened, potentially increasing file size and introducing color shifts and color artifacts.

-- Printing a PDF file to PostScript removes interactive features such as links, bookmarks, form data, Structured and Tagged PDF features, and Document Summary information.

-- Annotations are removed, although, if Printing Comments is enabled, their visual content is incorporated into the PDF pages.

-- You can't distill encrypted PDF files, such as those with security or digital signatures.

-- Acrobat Distiller converts ICC colorspaces in PDF files to PostScript CSAs (Color Space Arrays), which Distiller then converts back to ICC profiles. Image quality is lost because conversion between colorspaces and Color Space Arrays is lossy, especially with 4-component (that is, calibrated CMYK) ICC profiles.

-- Acrobat Distiller decompresses, and then recompresses, JPEG-compressed images, resulting in degraded image quality.

-- Distilling can degrade image resolution if compression or downsampling options are selected in the Job Options dialog box in Acrobat Distiller.

If you must redistill a PDF file, save the new PDF file in a different folder so that the original PDF file isn't overwritten.

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