Most PDF files are created from source material that is either generated in some form of Office software, like MS Office Word or Powerpoint, OpenOffice etc, or from a publishing system like Quark or InDesign. In almost all instances the underlying page size or sizes used are A4/US letter or smaller, in a fixed orientation (portrait or landscape). However, for files that are generated from graphics (drawing/design) packages or engineering systems, or from large-format old documents that have been scanned in, there is an often an issue with the page size.
In general, electronic display of documents on tablet devices is best handled with a relatively small underlying page size and/or the use of larger fonts. A5/half US Letter gives excellent results on most devices, and conversely, larger than A4/US Letter tends to result in files that cannot be read without zooming in on the page. Typically zooming-in makes reading the whole document/seeing the whole picture difficult and if printing is permitted (which in many cases it is not of course) then issues arise with print scaling which may prove unsurmountable. Zooming into very large pages (which is effectively an image zoom operation) is computationally demanding and may be slow or even impossible after a specific level of zooming on some devices (i.e. the software restricts the total zoom level owing to memory management or processing issues on the device).
There are a couple of solutions to these problems:
Scaling the source material: if the source material is a scanned image or a graphic, then the output PDF file created can be scaled to a selected underlying page size, e.g. A4/US Letter. This scaling can take place as part of the PDF file creation or, for image data, scaling can be carried out in the source application or image editor prior to printing to PDF. Obviously a scaled image may well be unreadable at the reduced size and/or may lose resolution in the scaling process, so a second option is worth considering.
Tiling the source material: instead of creating a single very large page a series of standard-sized pages can be created, with the large page spread across multiple standard-sized pages. This can be done in two ways – the source program may allow the output page size to be specified (e.g. via a Page Setup option) prior to creating the PDF file, so they resulting PDF is spread across several pages. Alternatively, and in many cases as a preferable option, the PDF can be generated with large page sizes and then the pages can be tiled using the tiling facility in Adobe Acrobat, as shown below. Typically the tiling process generates output for printing on a standard printer – i.e. one that handles pages up to A4/US Letter in size, which is the most common use for this facility, but you can specify the output as a PDF, and then a new PDF with tiled pages will be generated. An example can be seen: here…. Note that in this example I have specified a 10mm overlap which tells Adobe Acrobat to overlap the output pages and to include trim marks in the margins so it is easy to see how the pages fit together, and if printing is permitted, how to print and assemble a full-sized page from the tiled elements.