To complete your form you will have to save it to file first. Once it has been saved you can find the file and complete it. The file will save your changes as you go along once it is a file on your device. 

Apple - AAPL — Global Brands MatterHow to save email attachments on iPhone and iPad's 

Saving to iCloud

  1. Launch Mail from your Home screen.
  2. Choose the email that contains the attachment.
  3. Tap on the attachment attachment to bring up the Share sheet.
  4. File:Ei-share-apple.svg - Wikimedia Commons Tap the share sheet button on the bottom left of the page. It's a square with an upward arrow. 
  5. The File Manager For Ios 7 Goes Free For A Limited - Ios File Icon Png  Clipart (#1586891) - PinClipart Choose Save to Files.
  6. Icono de iCloud grande | Escaparate navideño, Fondos de palmeras, Disenos  de unasTap iCloud Drive to save to iCloud Drive or tap On My iPhone to save it directly to your phone.
  7. Tap Save on the top right of your screen.

Saving to Google Drive:

  1. Make sure you've downloaded the Gmail app.
  2. On your iPhone or iPad, open the Gmail app .
  3. Open the email message.
  4. Tap the attachment to open it.
  5. In the top right, tap Save to Drive Add to My Drive.
  6. When the message is saved, you'll see "Saved to Drive" on your screen.

Save email attachments to Dropbox

  1. Launch Mail from your Home screen.
  2. Choose the email that contains the attachment.
  3. Tap on the attachment attachment to bring up the Share sheet
  4. Choose Save to Dropbox.
  5. Select the folder to save your file to or Tap Choose a Folder You can't create a new folder on the fly using the Apple Share sheet, unfortunately.
  6. Tap Save.

Android icon - Transparent PNG & SVG vector fileHow to save email attachments on Android phones and tablets 

Downloading an attachment on Android

  1. On your Android phone or tablet, open the Gmail app .
  2. Open the email message.
  3. Tap Download Download.

Saving to Google Drive:

  1. On your Android phone or tablet, open the Gmail app .
  2. Open the email message.
  3. Tap Save to Drive Save to Drive.
  4. When the message is saved, you'll see "Saved to Drive" on your screen.