These files are all in pdf format. You may need an appropriate pdf reader, like Adobe Acrobat Reader, to view these files.
Some of the worksheets have fillable forms. When opened with most PDF readers, you will be able to add text and check boxes. Generally, you cannot use pdf forms directly in your browser, so you may need to download the file to fill out the worksheet.
For worksheets that ask you to draw, we suggest printing the pdf or using another sheet of paper.