How to combine multiple Illustrator files into one PDF?

Open the illustrator files in a single file by using each file in a separate "Artboard". (Artboard can add by the Artboards flyer by pressing New button)

Then save the file as a PDF. This will give you all in one PDF File and every artboard would be the new page in PDF file. 

1. Prepare the documents. Make sure you’ve made final edits and saved the files you want to combine.

2. Select the documents. In Adobe® Acrobat® Pro, choose File > Create > Combine Files Into A Single PDF. Make sure Single PDF is selected in the upper-right corner. Then, click Add Files, and choose Add Files or Add Folders. Select the files you want to combine, and click Add Files. You can combine PDF files, Microsoft® Word documents, Adobe InDesign® files, Microsoft Excel files, and files of just about any other format, in any combination. 

3. Arrange the files. In the Combine Files dialog box, rearrange the files so that they are listed in the order you want them to appear in the final PDF file. You can just drag a file to its new location, or select it and click Move Up or Move Down until it’s in the proper place.

Drag files to change their order in the final document. Tip: If you want to include only some of the pages in a document, select it and click Choose Pages. Then, select the pages you want to include.

Two ways to combine multiple Illustrator files in single (multi-page PDF)

1. Open all files you want to combine in illustrator, create new illustrator file, and enter the number of intended page(number of files intended to combine) in the "New Document" dialogue box. then copy (Ctrl+A then Ctrl+C/ Apple+A then Apple C) each illustrator artworks (ensure that non of the layers were locked to copy each objects) and paste it in the intended page/s of the new file ( Ctrl+V / Apple +V). Repeat it with the other files. once done copying, hit "Save as" and select PDF in the file format, choose your settings and done!

2. The easiest way is to open your Adobe Acrobat, click File, then select "create", then "Combine Files into single PDF" then select "add files or add folders" the select all the files you want to be included in your new PDF. You can arrange the pages in any order you want before saving it. Viola! you had created multiple paged PDF from Illustrator artworks!

Simple Paste in ONE word file and take a print using "DOPDF" software. You can simply take print without using MS. Word but you need mentioned software, easily available.

In Adobe Acrobat Pro, choose File > Create > Combine Files Into ASingle PDF. Make sure Single PDF is selected in the upper-right corner. Then, click Add Files, and choose Add Files or Add Folders. Select the files you want to combine, and click Add Files

Use Adobe Acrobat Professional. 

You can create different art boards in the same file and save as pdf.

or save each file as a pdf and combine in one file 

by using the software Icecream PDF split & merge we can do easily. 

 Adobe Illustrator CS2 and CS3 allows you to create multiple-page PDF files directly from the application using the Create Multi-Page PDF From Page Tiles option in the PDF Save dialog box when you save the file from Illustrator with tiled pages.

If you save Adobe Illustrator CS artwork with multiple-page tiles as an Adobe PDF file, the resulting PDF file contains one page, rather than individual pages for each tile. You can, however, convert Illustrator CS artwork with multiple-page tiles to a multiple-page PDF file by printing the file to PostScript, and then converting the PostScript file to PDF in Adobe Acrobat Distiller. To complete this process, you must have Illustrator CS, the Adobe PostScript Printer Driver, and Acrobat Distiller 5.x or later installed on your system. You can download the Adobe PostScript Printer Driver from the Adobe website atwww.adobe.com/support/downloads/.

To create multiple-page PDF files from an Illustrator file with multiple-page tiles:

In Illustrator CS2, CS3:

• In Illustrator, create a new document or open an existing Illustrator file with multiple-page tiles.
  • If you create a new document, specify a custom width and height large enough for all the pages in the PDF file in the New Document dialog box. For example, to create a four-page 8.5" x 11" document, enter 34 inches for Width and 11 inches for Height.
  • If you use an existing file with multiple-page tiles, proceed to step 8.
• Choose View > Show Page Tiling.
• Choose File > Print.
• In the Media section of the Print dialog box, select the orientation and the page size of the individual pages. For example, click Portrait Up in the Orientation section, and choose US Letter from the Size menu.
• Click Setup, and then choose Tile Full Pages from the Tiling menu.
• Click Done to close the Print dialog box. Illustrator numbers the pages from left to right and from top to bottom, starting with page 1. These page numbers appear on-screen for reference only.

Very easy, where special software to do so, such a program exist PDFMate