I have a PDF file, 1.26 MB (physical size). When I sent it to a wired printer, the window showed that file now had a size of 3.23 GB. What's going on here ?
From the following Microsoft Support Article: "The size of the EMF spool file may become very large when you print a document that contains lots of raster data"
Symptoms When you print a document that contains lots of raster data, the size of the Enhanced Metafile (EMF) spool file may become very large. Files such as Adobe .pdf files or Microsoft Word .doc/.docx documents may contain lots of raster data. Adobe .pdf files and Word .doc/.docx documents that contain gradients are even more likely to contain lots of raster data.
Cause This problem occurs because Graphics Device Interface (GDI) does not compress raster data when the GDI processes EMF spool files and generates EMF spool files.
This problem is very prominent with printers that support higher resolutions. The size of the raster data increases by four times if the dots-per-inch (dpi) in the file increases by two times. For example, a .pdf file of 1 megabyte (MB) may generate an EMF spool file of 500 MB. Therefore, you may notice that the printing process decreases in performance.
To resolve this problem, bypass EMF spooling. To do this, follow these steps:
1. Open the properties dialog box for the printer. 2. Click the Advanced tab. 3. Click the Print directly to the printer option.
Note This will disable all print processor-based features such as the following features:
- Booklet printing
- Driver collation
TL;DR - Your PDF file didn't increase in size. It is only a large spool file that was created. It's nothing to worry about but Microsoft provides a solution listed above to prevent that situation from happening again (with a reduction of features).
There are a number of reasons why a print file may be a lot larger than the original PDF/DOC/PPT, etc.
The first one applies particularly to files that started out as PowerPoint (PPT) presentations. A presentation typically has the same background graphics on every slide. In the PPT file (or a PDF created from it) that graphic only appears once, and every slide has a reference to it. In the print file, that same graphics will be added once for every slide. A 1 MB graphics in a 20 page page presentation will thus become 20 MB in the spool file. And it could be a lot larger, because of the next issue.
An image may grow when sent to a printer, depending on the printer model. Suppose you have a 1000 x 1000 pixel colour image. The displayed size of it is such that, when printed, it will show as 10" x 10". If you use a PCL5 or GDI printer that is set for 300 dpi, that image will be sent as a 3000 x 3000 pixel image (10 x 300) to account for the printer's resolution. So it is suddenly 9 times larger. This would not happen with PostScript printers, as they are capable of scaling images to suit.
Some people think that, if an image will be printed on a 1200 dpi printer, it needs to be scanned at 1200 dpi for best results, giving a size increase of 16 times compared to 300 dpi. In fact, for printing you only need 300 dpi, regardless of printer resolution. For most applications even 200 dpi will be perfectly adequate. Only for top-end prints (on a printer capable of 2400 dpi or better) would you scan at 600 dpi.
Note that here are no desktop printers capable of printing better than 1200 dpi (1440 dpi for some inkjets). Any higher quoted "resolution" is only intended to give an idea of the quality of the printer's halftoning (the ability to print shades of colour).
On Windows, what data (format) goes to the printer almost never is the same as the document format you create and edit or receive from someone.
(An exception may be an XPS document viewed in an XPS viewer being sent to an XPS-capable printer...)
The document format may be Excel/XLS(X), Word/DOC(X), PowerPoint/PPT(X), PDF, HTML, EPUB, whatever. No printer understands these formats. A printer requires some specific format(s) to be able to consume it and print it on paper.
The data transfered to the print device (and before transfer being spooled in a local folder) is different: On Windows the locally spooled file format is EMF ('Enhanced Meta File') or (O)XPS ('(Open) XML Paper Specification'). But these are are also not suitable for a printer. Also, it is not the original file which gets sent to the printer and then is no longer on your PC: it's a copy of the file, and that copy needs to be converted to suit the printer. It is the job of the Printer Driver to accomplish this conversion:
- a PostScript printer wants PostScript
- a PCL printer wants PCL
- an ESC/P printer wants ESCP
- an RCPS printer wants RPCS
- a raster printer wants raster data (many possible variants)
So some printer drivers will convert all pages to hi-res raster data, which takes a lot of bytes. And this is what you observe as the "increase" of file size, but mis-interpreted it: because your original document is still un-changed (in format as well as in file size).